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| python
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| DeepLearning or NLP
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| Other
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| Machine Learning
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| Mathematics
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I'm not sure what's the appropriate terminology here, but I'd like to have an application running passively that is ready to accept commands without having to reinitialize the whole thing.
The precise application is a machine learning system written in Python that takes a somewhat long time to train a classifier or to load a cached classifier. Once the classifier is loaded into memory, test cases or predictions made by the classifier happen very quickly.
I want to have to speed advantage of having the classifier already loaded into memory without having to reclassify/reload so that I can access the classifier quickly through other interfaces (command line, PHP, etc.).
This reminds me of asynchrony in Javascript, and I imagine some of the same underlying concepts are used here.
What's the best way to go about doing this?
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I made shoot em up like game.But I have only one ememy which fallows me on screen.But I want to make lots of enemys like each 10 second they will across on screen together 5 or 10 enemys.
ArrayList<Enemies> enemy = new ArrayList<Enemies>();
for (Enemies e : enemy) {
e.draw(g);
}
is it good creating array list and then showing on screen?
And Do I have to make some planing movements thoose enemies in my code ? I want that they vill appear not on same pozition.Like First 5 enemies will come top of screen then the other 5 or 10 enemies will come from left side.. so on.What is best solution for this?
And I have problem where to fullfiel this array like
enemy.add(new Enemies(750,60))
But this doesnt work ((
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I've been coding my way through Steve Kochan's Programming in Objective-C 2.0 book. I'm up to an exercise in chapter 7, ex 4, in case anyone has the book.
The question posed by the exercise it will the Fraction class written work with negative fractions such as -1/2 + -2/3?
Here's the implementation code in question -
@implementation Fraction
@synthesize numerator, denominator;
-(void) print
{
NSLog(@"%i/%i", numerator, denominator);
}
-(void) setTo: (int) n over: (int) d
{
numerator = n;
denominator = d;
}
-(double) convertToNum
{
if (denominator != 0)
return (double) numerator / denominator;
else
return 1.0;
}
-(Fraction *) add: (Fraction *) f
{
// To add two fractions:
// a/b + c/d = ((a * d) + (b * c)) / (b * d)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = (numerator * f.denominator) + (denominator * f.numerator);
resultDenom = denominator * f.denominator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(Fraction *) subtract: (Fraction *) f
{
// To subtract two fractions:
// a/b - c/d = ((a * d) - (b * c)) / (b * d)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = numerator * f.denominator - denominator * f.numerator;
resultDenom = denominator * f.denominator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(Fraction *) multiply: (Fraction *) f
{
// To multiply two fractions
// a/b * c/d = (a*c) / (b*d)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = numerator * f.numerator;
resultDenom = denominator * f.denominator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(Fraction *) divide: (Fraction *) f
{
// To divide two fractions
// a/b / c/d = (a*d) / (b*c)
// result will store the result of the addition
Fraction *result = [[Fraction alloc] init];
int resultNum, resultDenom;
resultNum = numerator * f.denominator;
resultDenom = denominator * f.numerator;
[result setTo: resultNum over: resultDenom];
[result reduce];
return result;
}
-(void) reduce
{
int u = numerator;
int v = denominator;
int temp;
while (v != 0) {
temp = u % v;
u = v;
v = temp;
}
numerator /= u;
denominator /= u;
}
@end
My question to you is will it work with negative fractions and can you explain how you know? Part of the issue is I don't know how to calculate negative fractions myself so I'm not too sure how to know.
Many thanks.
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I'm working on a simple subtraction problem, but unfortunately it keeps returning NaN
Here is the function
function subtraction(a, b) {
var regexp = /[$][,]/g;
a = a.replace(regexp, "");
b = b.replace(regexp, "");
var _a = parseFloat(a);
var _b = parseFloat(b);
return _a - _b;
}
And here is how I'm calling it.
txtGoodWill.value = subtraction(txtSellingPrice.value, txtBalanceSheet.value);
The numbers that get submitted to the function are ONLY Currency (IE: $2,000 or $20, etc)
Now I know that I cannot subtract numbers with a $ or a ,, but I can't for the life of me figure out why they are getting evaluated in the equasion.
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This is a simple jquery question: when my div #wrapper has a specific height (=browser height - 129px), i want to set the width of a inner div #object automatically too (cause I need a width for the object to read it out)
example of the html:
<div id="wrapper">
<div id="object"> </div>
</div>
example (jquery):
$("#wrapper").css({height:(($(window).height())-129)+'px'});
$("#object").css({width: [ CALCULATION ], height: ($("#wrapper").height())+'px'})
the original proportion of the image is: 1600x1080
here's the link to the attachment, take a look at it (tinypic):
http://www.imgplace.com/...age1.png
additonal information:
the heights 500px, 600px and 700px you can see in the attachment are just examples, the heigth could also be 711px, 623px, 998px etc.
My math skills aren't really good, would be great if someone could help me out
Kind Regards,
Hans :-)
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I am using JQuery to get the contents of a div, which only contains a price in dollars and I would like to add $99 to it, but its text, so when I do the below it won't work.
$('#price_' + part[0]).text($('#price_' + part[0]).text() + 99);
//Changes the div contents to $10099 - if it the contents was $100 to start with
So the question is how can I add the numeric values?
Thanks all
Edit
Please note some numbers can contain a comma i.e. $1,200
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If I have this:
A * f = g;
A: upper triangular matrix (n x n)
f: (n x 1)
g: (n x 1)
Need to solve for f using back substitution algorithm. I would say that it not really that hard to write one myself, but oh well, if there is a library out there, then why not.
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I have a arbitrarily large string of text from the user that needs to be split into 10k chunks (potentially adjustable value) and sent off to another system for processing.
Chunks cannot be longer than 10k (or other arbitrary value)
Text should be broken with natural language context in mind
split on punctuation when possible
split on spaces if no punction exists
break a word as a last resort
I'm trying not to re-invent the wheel with this, any suggestions before I roll this from scratch?
Using C#.
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I like to add (+1) to a number. But problem is my number can sometimes have 0 preceding it. Like 01, 02, 03, 04. So I like result to be:
mockup01 + 1 = mockup02
mockup11 + 1 = mockup12
How can that be achieved? Example of how I would use it would be if I had filename named mockup_01.htm and change it to mockup_02.htm
Thanks!
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i'm working on a project and need your ideas, advices.
First of all, let me tell my problem.
There is power button and some other keys of a machine and
there is only one user has authentication to use this machine.There are
no other authentication methods, the machine is in public area in a company.
the machine is working with the combination of pressing power button and some other keys.
The order of pressing keys is secret but we don't trust it, anybody can learn the password and can access the machine.
i have the capability of managing the key hold time and also some other metrics to
measure the time differences between the key such as horizantal or vertical key press times (differences). and also i can measure the hold time etc.
These all means i have some inputs,
Now i'm trying to get a user profile by analysing these inputs.
My idea is to get the authenticated user to press the password n times and create a threshold or something similar to that.
This method also can be said BIOMETRICS, anyone else who knows the machine button combination, can try the password but if he is out of this range can not get access it.
How can i adapt these into my algorithms? where should i start ?
i don't want to delve deep into machine learning, and also i can see that in my first try i can get false positive and false negative values really high, but i can manage it by changing my inputs.
thanks.
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I'm using the explorer feature of Weka for classification.
So I have my .arff file, with 2 features of NUMERIC value, and my class is a binary 0 or 1 (eg {0,1}).
Sample:
@RELATION summary
@ATTRIBUTE feature1 NUMERIC
@ATTRIBUTE feature2 NUMERIC
@ATTRIBUTE class {1,0}
@DATA
23,11,0
20,100,1
2,36,0
98,8,1
.....
I load this .arff file, use 10-fold cross validation (no test file), and choose NaiveBayes, then I classify the data, and it gives me: 5 incorrectly labeled, 100 correctly labeled. So far so good.
Now, I significantly change my .arff file (give completely random values for my feature attributes). And repeat the above, and I get the EXACT same statistics when classifying.
I tried this with more changes to my .arff file, different classification algorithms. Still, EXACT same statistic (within the same algorithm) no matter what values I give to my .arff file.
Am I doing something wrong here?
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I want to project my Polygon along a vector to a plane in 3d Space. I would preferably use a single transformation matrix to do this, but I don't know how to build a matrix of this kind.
Given
the plane's parameters (ax+by+cz+d),
the world coordinates of my Polygon. As stated in the the headline, all vertices of my polygon lie in another plane.
the direction vector along which to project my Polygon (currently the polygon's plane's normal vector)
goal
-a 4x4 transformation matrix which performs the required projection,
or
some insight on how to construct one myself
UPDATE
Thank you for the answer, it works as intended.
A word of caution to the people who found this: If the Plane of projection's normal is parallel to the projection vector, the Denominator D will become (almost) 0, so to avoid strange things from happening, some kind of handling for this special case is needed. I solved it by checking if D < 1e-5, and if so, just translate my polygon along hte extrusion vector.
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From Wikipedia, camera resectioning is the process of finding the true parameters of the camera that produced a given photograph or video. Camera resectioning is also known as geometric camera calibration.
Currently I am using Camera Calibration Toolbox for Matlab for my camera calibration. The toolbox returns calibration parameters such as focal length, principle point, skew, and distortion. However, the issue with this method is that it requires an extra step in calibrating the camera by using a special calibration object like a checkerboard. Additionally, it only works for one focus of the camera.
How can I get the calibration parameters without manually calibrating? For example, how does Microsoft's Photosynth perform camera calibration on its images?
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I'm trying to work out a problem I'm having with degrees. I have data that is a list of of angles, in standard degree notation -- e.g. 26 deg.
Usually when dealing with angles, if an angle exceeds 360 deg then the angle continues around and effectively "resets" -- i.e. the angle "starts again", e.g. 357 deg, 358 deg, 359 deg, 0 deg, 1 deg, etc. What I want to happen is the degree to continue increasing -- i.e. 357 deg, 358 deg, 359 deg, 360 deg, 361 deg, etc. I want to modify my data so that I have this converted data in it.
When numbers approach the 0 deg limit, I want them to become negative -- i.e. 3 deg, 2 deg, 1 deg, 0 deg, -1 deg, -2 deg, etc.
With multiples of 360 deg (both positive and negative), I want the degrees to continue, e.g. 720 deg, etc.
Any suggestions on what approach to take? There is, no doubt, a frustratingly simple way of doing this, but my current solution is kludgey to say the least .... ! My best attempt to date is to look at the percentage difference between angle n and angle n - 1. If this is a large difference -- e.g. > 60% -- then this needs to be modified, by adding or subtracting 360 deg to the current value, depending on the previous angle value. That is, if the previous angle is negative, substract 360, and add 360 if the previous angle is positive.
Any suggestions on improving this? Any improvements?
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Problem Constraints
Size of the data set, but not the data itself, is known.
Data set grows by one data point at a time.
Trend line is graphed one data point at a time (using a spline/Bezier curve).
Graphs
The collage below shows data sets with reasonably accurate trend lines:
The graphs are:
Upper-left. By hour, with ~24 data points.
Upper-right. By day for one year, with ~365 data points.
Lower-left. By week for one year, with ~52 data points.
Lower-right. By month for one year, with ~12 data points.
User Inputs
The user can select:
the type of time series (hourly, daily, monthly, quarterly, annual); and
the start and end dates for the time series.
For example, the user could select a daily report for 30 days in June.
Trend Weight
To calculate the window size (i.e., the number of data points to average when calculating the trend line), the following expression is used:
data points / trend weight
Where data points is derived from user inputs and trend weight is 6.4. Even though a trend weight of 6.4 produces good fits, it is rather arbitrary, and might not be appropriate for different user inputs.
Question
How should trend weight be calculated given the constraints of this problem?
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In .NET what is the best way to find the length of an integer in characters if it was represented as a string?
e.g.
1 = 1 character
10 = 2 characters
99 = 2 characters
100 = 3 characters
1000 = 4 characters
The obvious answer is to convert the int to a string and get its length but I want the best performance possible without the overhead of creating a new string.
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I think this is an interesting question, at least for me.
I have a list of words, let's say:
photo, free, search, image, css3, css, tutorials, webdesign, tutorial, google, china, censorship, politics, internet
and I have a list of contexts:
Programming
World news
Technology
Web Design
I need to try and match words with the appropriate context/contexts if possible.
Maybe discovering word relationships in some way.
Any ideas?
Help would be much appreciated!
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I am looking for a method to build a hierarchy of words.
Background: I am a "amateur" natural language processing enthusiast and right now one of the problems that I am interested in is determining the hierarchy of word semantics from a group of words.
For example, if I have the set which contains a "super" representation of others, i.e.
[cat, dog, monkey, animal, bird, ... ]
I am interested to use any technique which would allow me to extract the word 'animal' which has the most meaningful and accurate representation of the other words inside this set.
Note: they are NOT the same in meaning. cat != dog != monkey != animal
BUT cat is a subset of animal and dog is a subset of animal.
I know by now a lot of you will be telling me to use wordnet. Well, I will try to but I am actually interested in doing a very domain specific area which WordNet doesn't apply because:
1) Most words are not found in Wordnet
2) All the words are in another language; translation is possible but is to limited effect.
another example would be:
[ noise reduction, focal length, flash, functionality, .. ]
so functionality includes everything in this set.
I have also tried crawling wikipedia pages and applying some techniques on td-idf etc but wikipedia pages doesn't really do much either.
Can someone possibly enlighten me as to what direction my research should go towards? (I could use anything)
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Is there a fast method for taking the modulus of a floating point number?
With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31-1 without needing division. integer trick
Can any similar tricks be applied for floating point numbers?
Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. This rules out using integer calculations on the floating point data.
The primes I'm interested in would be 2^7-1 and 2^31-1, although if there are more efficient ones for floating point numbers, those would be welcome.
One intended use of this algorithm would be to calculate a running "checksum" of input floating point numbers as they are being read into an algorithm. To avoid taking up too much of the calculation capability, I'd like to keep this lightweight.
Apparently a similar technique is used for larger numbers, particularly 2^127 - 1. Unfortunately, the math in the paper is beyond me, and I haven't been able to figure out how to convert it to smaller primes.
Example of floating point MOD 2^127 - 1 - HASH127
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This is more of a maths question than programming but I figure a lot of people here are pretty good at maths! :)
My question is: Given a 9 x 9 grid (81 cells) that must contain the numbers 1 to 9 each exactly 9 times, how many different grids can be produced. The order of the numbers doesn't matter, for example the first row could contain nine 1's etc. This is related to Sudoku and we know the number of valid Sudoku grids is 6.67×10^21, so since my problem isn't constrained like Sudoku by having to have each of the 9 numbers in each row, column and box then the answer should be greater than 6.67×10^21.
My first thought was that the answer is 81! however on further reflection this assumes that the 81 numbers possible for each cell are different, distinct number. They are not, there are 81 possible numbers for each cell but only 9 possible different numbers.
My next thought was then that each of the cells in the first row can be any number between 1 and 9. If by chance the first row happened to be all the same number, say all 1s, then each cell in the second row could only have 8 possibilites, 2-9. If this continued down until the last row then number of different permutations could be calculated by 9^2 * 8^2 * 7^2 ..... * 1^2. However this doesn't work if each row doesn't contain 9 of the same number.
It's been quite a while since I studied this stuff and I can't think of a way to work it out, I'd appreciate any help anyone can offer.
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I am in charge of a program that is used to create a set of nodes and paths for consumption by an autonomous ground vehicle. The program keeps track of the locations of all items in its map by indicating the item's position as being x meters north and y meters east of an origin point of 0,0. In the real world, the vehicle knows the location of the origin's lat and long, as it is determined by a dgps system and is accurate down to a couple centimeters. My program is ignorant of any lat long coordinates.
It is one of my goals to modify the program to keep track of lat long coords of items in addition to an origin point and items' x,y position in relation to that origin. At first blush, it seems that I am going to modify the program to allow the lat long coords of the origin to be passed in, and after that I desire that the program will automatically calculate the lat long of every item currently in a map. From what I've researched so far, I believe that I will need to figure out the math behind converting to lat long coords from a UTM like projection where I specify the origin points and meridians etc as opposed to whatever is defined already for UTM.
I've come to ask of you GIS programmers, am I on the right track? It seems to me like there is so much to wrap ones head around, and I'm not sure if the answer isn't something as simple as, "oh yea theres a conversion from meters to lat long, here"
Currently, due to the nature of DGPS, the system really doesn't need to care about locations more than oh, what... 40 km? radius away from the origin. Given this, and the fact that I need to make sure that the error on my coordinates is not greater than .5 meters, do I need anything more complex than a simple lat/long to meters conversion constant?
I'm knee deep in materials here. I could use some pointers about what concepts to research.
Thanks much!
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In a two dimentional integer space, you have two points, A and B. This function returns an enumeration of the points in the quadrilateral subset bounded by A and B.
A = {1,1} B = {2,3}
Fn(A,B) = {{1,1},{1,2},{1,3},{2,1},{2,2},{2,3}}
I can implement it in a few lines of LINQ.
private void UnknownFunction(Point to, Point from, List<Point> list)
{
var vectorX = Enumerable.Range(Math.Min(to.X, from.X), Math.Abs(to.X - from.Y) + 1);
var vectorY = Enumerable.Range(Math.Min(to.Y, from.Y), Math.Abs(to.Y - from.Y) + 1);
foreach (var x in vectorX)
foreach (var y in vectorY)
list.Add(new Point(x, y));
}
I'm fairly sure that this is a standard mathematical operation, but I can't think what it is.
Feel free to tell me that it's one line of code in your language of choice. Or to give me a cunning implementation with lambdas or some such.
But mostly I just want to know what it's called. It's driving me nuts.
It feels a little like a convolution, but it's been too long since I was at school for me to be sure.
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Has anyone seen this weird value while handling sin / cos/ tan / acos.. math stuff?
===THE WEIRD VALUE===
-1.#IND00
=====================
void inverse_pos(double x, double y, double& theta_one, double& theta_two)
{
// Assume that L1 = 350 and L2 = 250
double B = sqrt(x*x + y*y);
double angle_beta = atan2(y, x);
double angle_alpha = acos((L2*L2 - B*B - L1*L1) / (-2*B*L1));
theta_one = angle_beta + angle_alpha;
theta_two = atan2((y-L1*sin(theta_one)), (x-L1*cos(theta_one)));
}
This is the code I was working on.
In a particular condition - like when x & y are 10 & 10,
this code stores -1.#IND00 into theta_one & theta_two.
It doesn't look like either characters or numbers :(
Without a doubt, atan2 / acos / stuff are the problems.
But the problem is, try and catch doesn't work either
cuz those double variables have successfully stored
some values in them.
Moreover, the following calculations never complain about it
and never break the program!
I'm thinking of forcing to use this value somehow and make the entire program crash...
So that I can catch this error..
Except for that idea, I have no idea how I should check whether these
theta_one and theta_two variables have stored this crazy values.
Any good ideas?
Thank you in advance..
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I'm trying to round a number to it's first decimal place and, considering the different MidpointRounding options, that seems to work well. A problem arises though when that number has sunsequent decimal places that would arithmetically affect the rounding.
An example:
With 0.1, 0.11..0.19 and 0.141..0.44 it works:
Math.Round(0.1, 1) == 0.1
Math.Round(0.11, 1) == 0.1
Math.Round(0.14, 1) == 0.1
Math.Round(0.15, 1) == 0.2
Math.Round(0.141, 1) == 0.1
But with 0.141..0.149 it always returns 0.1, although 0.146..0.149 should round to 0.2:
Math.Round(0.145, 1, MidpointRounding.AwayFromZero) == 0.1
Math.Round(0.146, 1, MidpointRounding.AwayFromZero) == 0.1
Math.Round(0.146, 1, MidpointRounding.ToEven) == 0.1
Math.Round(0.146M, 1, MidpointRounding.ToEven) == 0.1M
Math.Round(0.146M, 1, MidpointRounding.AwayFromZero) == 0.1M
I tried to come up with a function that addresses this problem, and it works well for this case, but of course it glamorously fails if you try to round i.e. 0.144449 to it's first decimal digit (which should be 0.2, but results 0.1.) (That doesn't work with Math.Round() either.)
private double "round"(double value, int digit)
{
// basically the old "add 0.5, then truncate to integer" trick
double fix = 0.5D/( Math.Pow(10D, digit+1) )*( value >= 0 ? 1D : -1D );
double fixedValue = value + fix;
// 'truncate to integer' - shift left, round, shift right
return Math.Round(fixedValue * Math.Pow(10D, digit)) / Math.Pow(10D, digit);
}
I assume a solution would be to enumerate all digits, find the first value larger than 4 and then round up, or else round down. Problem 1: That seems idiotic, Problem 2: I have no idea how to enumerate the digits without a gazillion of multiplications and subtractios.
Long story short: What is the best way to do that?
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I m looking for a faster implementation or good a approximation of functions provided by cmath.
I need to speed up the following functions
pow(x,y)
exp(z*pow(x,y))
where z<0. x is from (-1.0,1.0) and y is from (0.0, 5.0)
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How do I project the X axis to a plane if the plane is defined by three points?
The default local 1-direction is the projection of the global x-axis onto the surface. If the global x-axis is within 0.1° of being normal to the surface, the local 1-direction is the projection of the global z-axis onto the surface.
Let's suppose that these points are:
t1 = [-0.362879991531372, 0.357021987438202, -0.373737007379532]
t2 = [-0.383525013923645, 0.371621012687683, -0.383549988269806]
t3 = [-0.383534014225006, 0.34629300236702, -0.38544899225235]
Is the vector [0.78280971952246, -0.0307519963686645, 0.411184845614438] correct answer in this case? I've calculated the angle between the surf and x (1,0,0) is ~28°.
And can you give the entire procedure for the calculation, because I'm just puzzled.
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Hello all math masters, I got a problem for you:
I have a 2D game (top down), and I would like to make the character escape from a shot, but not just walk away from the shot (I mean, don't be pushed by the shot), I want it to have a good dodging skills.
The variables are:
shotX - shot x position
shotY - shot y position
shotSpeedX - shot x speed
shotSpeedY - shot x speed
charX - character x position
charY - character y position
keyLeft - Set to true to make the character press the to left key
keyRight - Set to true to make the character press the to right key
keyUp - Set to true to make the character press the to up key
keyDown - Set to true to make the character press the down key
I can understand the following languages:
C/C++
Java
Actionscript 2/3
Javascript
I got this code (Actionscript 3), but sometimes it doesn't work:
var escapeToLeft:Boolean = false;
var r:Number = Math.atan2(0 - shotSpeedY, 0 - shotSpeedX)
var angle:Number = Math.atan2(charY - (shotY + shotSpeedY), charX - (shotX + shotSpeedX));
var b:Number = diepix.fixRotation(r-angle); // This function make the number between -180 and 180
if(b<0) {
escapeToLeft = true;
}
r += (escapeToLeft?1:0 - 1) * Math.PI / 2;
var cx:Number = Math.cos(r);
var cy:Number = Math.sin(r);
if(cx < 0.0) {
keyLeft = true;
}else {
keyRight = true;
}
if(cy < 0.0) {
keyUp = true;
}else {
keyDown = true;
}
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I had used several ways to do some simple integer arithmetic in BASH (3.2). But I can't figure out the best (preferred) way to do it.
result=`expr 1 + 2`
result=$(( 1 + 2 ))
let "result = 1 + 2"
What are the fundamental differences between those expressions?
Is there other ways to do the same?
Is the use of a tool like bc mandatory for floating point arithmetic?
result=`echo "7/354" | bc`
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I have a what I think is a simple machine learning question.
Here is the basic problem: I am repeatedly given a new object and a list of descriptions about the object. For example: new_object: 'bob' new_object_descriptions: ['tall','old','funny']. I then have to use some kind of machine learning to find previously handled objects that have the 10 or less most similar descriptions, for example, past_similar_objects: ['frank','steve','joe']. Next, I have an algorithm that can directly measure whether these objects are indeed similar to bob, for example, correct_objects: ['steve','joe']. The classifier is then given this feedback training of successful matches. Then this loop repeats with a new object.
a
Here's the pseudo-code:
Classifier=new_classifier()
while True:
new_object,new_object_descriptions = get_new_object_and_descriptions()
past_similar_objects = Classifier.classify(new_object,new_object_descriptions)
correct_objects = calc_successful_matches(new_object,past_similar_objects)
Classifier.train_successful_matches(object,correct_objects)
But, there are some stipulations that may limit what classifier can be used:
There will be millions of objects put into this classifier so classification and training needs to scale well to millions of object types and still be fast. I believe this disqualifies something like a spam classifier that is optimal for just two types: spam or not spam. (Update: I could probably narrow this to thousands of objects instead of millions, if that is a problem.)
Again, I prefer speed when millions of objects are being classified, over accuracy.
Update: The classifier should return the 10 (or fewer) most similar objects, based on feedback from past training. Without this limit, an obvious cheat would be for the classifier could just return all past objects :)
What are decent, fast machine learning algorithms for this purpose?
Note: The calc_successful_matches distance metric is extremely expensive to calculate and that's why I'm using a fast machine learning algorithm to try to guess which objects will be close before I actually do the expensive calculation.
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I have a system that stores vectors and allows a user to find the n most similar vectors to the user's query vector. That is, a user submits a vector (I call it a query vector) and my system spits out "here are the n most similar vectors." I generate the similar vectors using a KD-Tree and everything works well, but I want to do more. I want to present a list of the n most similar vectors even if the user doesn't submit a complete vector (a vector with missing values). That is, if a user submits a vector with three dimensions, I still want to find the n nearest vectors (stored vectors are of 11 dimensions) I have stored.
I have a couple of obvious solutions, but I'm not sure either one seem very good:
Create multiple KD-Trees each built using the most popular subset of dimensions a user will search for. That is, if a user submits a query vector of thee dimensions, x, y, z, I match that query to my already built KD-Tree which only contains vectors of three dimensions, x, y, z.
Ignore KD-Trees when a user submits a query vector with missing values and compare the query vector to the vectors (stored in a table in a DB) one by one using something like a dot product.
This has to be a common problem, any suggestions? Thanks for the help.
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How do I check if an element a belongs to a specific cyclic group G of prime order, given the generator? Right now i simply generate all the elements in the group, save them into a container and check if the element is in it. This is the code im currently using to generate all the elements of the group:
public HashSet<BigInteger> group_elements(BigInteger g, BigInteger q) {
HashSet<BigInteger> group = new HashSet<BigInteger>();
BigInteger element = modPow(g,ONE,q);
for (int i = 2; !group.contains(element); i++) {
group.add(element);
element = modPow(g, BigInteger.valueOf(i), q);
}
return group;
}
And to see if a element is in the group i simply check:
if (group.contains(num)) { ... }
As you can see the language is Java
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How do I calculate a curve of a linear floating point number (0 to 1) and get another floating point number as a result? What I want is up until the half (0..0.5), to be inversed logarithmic and high than that to be logarithmic like a curve according to the given linear value.
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I have a yes/no classification problem, where false positives are worse than false negatives.
Is there a way to implement this fact into neural network especially in MATLAB's Neural Network Toolbox?
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I have four integer numbers a, b, c, d, and integer x ϵ [1, 40].
How do I find the values of {a, b, c, d}, for which one of following equations is true for any 1 <= x <= 40?
x = a or
x = b or
x = a + b or
x = a + b + c + d or
x + a = c + d or
x + a + b = c + d or
...
x + a + b + c = d or ...
Example:
If x = 17, by {a = 1, b = 2, c = 5, d = 15}, I can write x + a + b = c + d
The question is to present any x ϵ [1, 40] by {a, b, c, d}.
Update:
There is only one solution, I'm sure, and I think, that
{a = 1; a + b + c + d = 40}
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Can anyone tell me how do this? They are already integers, so I'm not sure what to try...
var lrgSlideShow = {
activeClass: 'active',
wrapperClass: 'slideshow-widget-large',
pauseLength: 2000,
fadeLength: 1000
}
setInterval(changeImg,lrgSlideShow.pauseLength+lrgSlideShow.fadeLength);
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I have two Cartesian coordinates. There are xyz and BIG XYZ. I want to make these are parallel to each other. For example, x paralel to X ,y parallel to Y and z paralel to Z. I use a rotation matrix but I have a lot of different rotation matrices. For example I have 3D point in xyz Cartesian coordinates and it's called A and I want to change Cartesian coordinate to BIG XYZ and find the same 3D point in this coordinates its called B. Until now it is okay. But when I used a different rotational matrix, points were changed. What can I do? Which Euler rotations can I use?
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I have a couple of numerical datasets that I need to create a concept hierarchy for. For now, I have been doing this manually by observing the data (and a corresponding linechart). Based on my intuition, I created some acceptable hierarchies.
This seems like a task that can be automated. Does anyone know if there is an algorithm to generate a concept hierarchy for numerical data?
To give an example, I have the following dataset:
Bangladesh 521
Brazil 8295
Burma 446
China 3259
Congo 2952
Egypt 2162
Ethiopia 333
France 46037
Germany 44729
India 1017
Indonesia 2239
Iran 4600
Italy 38996
Japan 38457
Mexico 10200
Nigeria 1401
Pakistan 1022
Philippines 1845
Russia 11807
South Africa 5685
Thailand 4116
Turkey 10479
UK 43734
US 47440
Vietnam 1042
for which I created the following hierarchy:
LOWEST ( < 1000)
LOW (1000 - 2500)
MEDIUM (2501 - 7500)
HIGH (7501 - 30000)
HIGHEST ( > 30000)
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I have this code:
CGPoint arrowMiddle = CGPointMake((arrowOne.x + arrowTo.x)/2, (arrowOne.y + arrowTo.y)/2);
CGPoint arrowLeft = CGPointMake(arrowMiddle.x-40, arrowMiddle.y);
CGPoint arrowRight = CGPointMake(arrowMiddle.x, arrowMiddle.y + 40);
[arrowPath addLineToScreenPoint:arrowLeft];
[arrowPath addLineToScreenPoint:arrowMiddle];
[arrowPath addLineToScreenPoint:arrowRight];
[[mapContents overlay] addSublayer:arrowPath];
[arrowPath release];
with this output:
http://img517.yfrog.com/img517/7690/schermafbeelding2010032.png
What have i to add to get the left and right the at same degree of the line + 30°.
If someone has the algorithm of drawing an arrow on a line, pleas give it. It doesn't matter what programming language it is...
Thanks
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Greetings everybody. I have seen examples of such operations for so many times that I begin to think that I am getting something wrong with binary arithmetic. Is there any sense to perform the following:
byte value = someAnotherByteValue & 0xFF;
I don't really understand this, because it does not change anything anyway. Thanks for help.
P.S.
I was trying to search for information both elsewhere and here, but unsuccessfully.
EDIT:
Well, off course i assume that someAnotherByteValue is 8 bits long, the problem is that i don't get why so many people ( i mean professionals ) use such things in their code. For example in SharpZlib there is:
buffer_ |= (uint)((window_[windowStart_++] & 0xff |
(window_[windowStart_++] & 0xff) << 8) << bitsInBuffer_);
where window_ is a byte buffer.
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I have the following piece of pseudo-C/Java/C# code:
int a[]= { 30, 20 };
int b[] = { 40, 50 };
int c[] = {12, 12};
How do I compute the cross-product ABxAC?
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I have written some general functions to convert between decimal and any other base-n number system(n<=36 for now) and vice-versa. Don't want to make things messy here so i have posted the code here.
Could anybody suggest any better way for this? May be more effective and Rubyish?
Thanks
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Try running this in a .VBS file
MsgBox(545.14-544.94)
You get a neat little answer of 0.199999999999932!
This rounding issue also occurs unfortunately in Sin(2 * pi) since VB can only ever see the (user defined) variable pi as accurate as 3.14159265358979.
Is rounding it manually (and loosing accuracy) the only way to improve the result? What is the most effective way of dealing with this kind of problem?
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I am having a real headache trying to set a node's local position to match a given world position.
I was given a solution but, AFAICS, it only takes into account orientation and position but NOT scaling :
node_new_local_position = node_parent.derivedOrientation().Inverse() * ( world_position_to_match - node_parent.derivedPosition() );
The node in question is a child of node_parent; node_parent local and derived properties (orientation, position and scaling) are known, as well as its full matrix transform.
All the positions are 3d vectors; the orientation is a quaternion; the full transform is a 4x4 matrix.
Could someone please help me to modify the solution to support scaling in the node hierarchy?
Many thanks in advance,
Bill
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How to create the transformation matrix (4x4) that transforms a cylinder (of height 1 and diameter 1) into a cone that represents my spotlight (position, direction and cutoff angle) ?
--edit--
In other words: how to draw the cone that represents my spotlight by drawing a cylinder through a suitable transformation matrix.
--edit2--
The following (pseudo)code gives me the expected result:
PushMatrix();
LoadIdentity();
Perspective(lightCutoffAngle * 2, 1, 0.001, 10000); // fov, aspect, near, far
LookAt(lightPos.x,lightPos.y,lightPos.z, lightDir.x,lightDir.y,lightDir.z, 0,0,1);
Matrix44 mat = GetModelViewMatrix();
mat.Invert();
PopMatrix();
MultMatrix(mat);
DrawCone(1,1); // diameter, height
HIH
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I'm using .net WPF geometry classes to graph waveforms. I've been using the matrix transformations to convert from the screen coordinate space to my coordinate space for the waveform. Everything works great and it's really simple to keep track of my window and scaling, etc. I can even use the inverse transform to calculate the mouse position in terms of the coordinate space. I use the built in Scaling and Translation classes and then a custom matrix to do the y-axis flipping (there's not a prefab matrix for flipping). I want to be able to graph these waveforms on a log scale as well (either x axis or y axis or both), but I'm not sure if this is even possible to do with a matrix transformation. Does anyone know if this is possible, and if it is, what is the matrix?
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I'm trying to calculate the sunset / rise times using python based on the link provided below.
My results done through excel and python do not match the real values. Any ideas on what I could be doing wrong?
My Excel sheet can be found under .. http://transpotools.com/sun_time.xls
# Created on 2010-03-28
# @author: dassouki
# @source: [http://williams.best.vwh.net/sunrise_sunset_algorithm.htm][2]
# @summary: this is based on the Nautical Almanac Office, United States Naval
# Observatory.
import math, sys
class TimeOfDay(object):
def calculate_time(self, in_day, in_month, in_year,
lat, long, is_rise, utc_time_zone):
# is_rise is a bool when it's true it indicates rise,
# and if it's false it indicates setting time
#set Zenith
zenith = 96
# offical = 90 degrees 50'
# civil = 96 degrees
# nautical = 102 degrees
# astronomical = 108 degrees
#1- calculate the day of year
n1 = math.floor( 275 * in_month / 9 )
n2 = math.floor( ( in_month + 9 ) / 12 )
n3 = ( 1 + math.floor( in_year - 4 * math.floor( in_year / 4 ) + 2 ) / 3 )
new_day = n1 - ( n2 * n3 ) + in_day - 30
print "new_day ", new_day
#2- calculate rising / setting time
if is_rise:
rise_or_set_time = new_day + ( ( 6 - ( long / 15 ) ) / 24 )
else:
rise_or_set_time = new_day + ( ( 18 - ( long/ 15 ) ) / 24 )
print "rise / set", rise_or_set_time
#3- calculate sun mean anamoly
sun_mean_anomaly = ( 0.9856 * rise_or_set_time ) - 3.289
print "sun mean anomaly", sun_mean_anomaly
#4 calculate true longitude
true_long = ( sun_mean_anomaly +
( 1.916 * math.sin( math.radians( sun_mean_anomaly ) ) ) +
( 0.020 * math.sin( 2 * math.radians( sun_mean_anomaly ) ) ) +
282.634 )
print "true long ", true_long
# make sure true_long is within 0, 360
if true_long < 0:
true_long = true_long + 360
elif true_long > 360:
true_long = true_long - 360
else:
true_long
print "true long (360 if) ", true_long
#5 calculate s_r_a (sun_right_ascenstion)
s_r_a = math.degrees( math.atan( 0.91764 * math.tan( math.radians( true_long ) ) ) )
print "s_r_a is ", s_r_a
#make sure it's between 0 and 360
if s_r_a < 0:
s_r_a = s_r_a + 360
elif true_long > 360:
s_r_a = s_r_a - 360
else:
s_r_a
print "s_r_a (modified) is ", s_r_a
# s_r_a has to be in the same Quadrant as true_long
true_long_quad = ( math.floor( true_long / 90 ) ) * 90
s_r_a_quad = ( math.floor( s_r_a / 90 ) ) * 90
s_r_a = s_r_a + ( true_long_quad - s_r_a_quad )
print "s_r_a (quadrant) is ", s_r_a
# convert s_r_a to hours
s_r_a = s_r_a / 15
print "s_r_a (to hours) is ", s_r_a
#6- calculate sun diclanation in terms of cos and sin
sin_declanation = 0.39782 * math.sin( math.radians ( true_long ) )
cos_declanation = math.cos( math.asin( sin_declanation ) )
print " sin/cos declanations ", sin_declanation, ", ", cos_declanation
# sun local hour
cos_hour = ( math.cos( math.radians( zenith ) ) -
( sin_declanation * math.sin( math.radians ( lat ) ) ) /
( cos_declanation * math.cos( math.radians ( lat ) ) ) )
print "cos_hour ", cos_hour
# extreme north / south
if cos_hour > 1:
print "Sun Never Rises at this location on this date, exiting"
# sys.exit()
elif cos_hour < -1:
print "Sun Never Sets at this location on this date, exiting"
# sys.exit()
print "cos_hour (2)", cos_hour
#7- sun/set local time calculations
if is_rise:
sun_local_hour = ( 360 - math.degrees(math.acos( cos_hour ) ) ) / 15
else:
sun_local_hour = math.degrees( math.acos( cos_hour ) ) / 15
print "sun local hour ", sun_local_hour
sun_event_time = sun_local_hour + s_r_a - ( 0.06571 *
rise_or_set_time ) - 6.622
print "sun event time ", sun_event_time
#final result
time_in_utc = sun_event_time - ( long / 15 ) + utc_time_zone
return time_in_utc
#test through main
def main():
print "Time of day App "
# test: fredericton, NB
# answer: 7:34 am
long = 66.6
lat = -45.9
utc_time = -4
d = 3
m = 3
y = 2010
is_rise = True
tod = TimeOfDay()
print "TOD is ", tod.calculate_time(d, m, y, lat, long, is_rise, utc_time)
if __name__ == "__main__":
main()
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I'm interested in data mining projects, and have always wanted to create a classification algorithm that would determine which specific check-ins need code-reviews, and which may not.
I've developed many heuristics for my algorithm, although I've yet to figure out the killer...
How can I programmatically check the computational complexity of a chunk of code?
Furthermore, and even more interesting - how could I use not just the code but the diff that the source control repository provides to obtain better data there..
IE: If I add complexity to the code I'm checking in - but it reduces complexity in the code that is left - shouldn't that be considered 'good' code?
Interested in your thoughts on this.
UPDATE
Apparently I wasn't clear. I want this
double codeValue = CodeChecker.CheckCode(someCodeFile);
I want a number to come out based on how good the code was. I'll start with numbers like VS2008 gives when you calculate complexity, but would like to move to further heuristics.
Anyone have any ideas? It would be much appreciated!
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I'm struggling my way through Artificial Intelligence: A Modern Approach in order to alleviate my natural stupidity. In trying to solve some of the exercises, I've come up against the "Who Owns the Zebra" problem, Exercise 5.13 in Chapter 5. This has been a topic here on SO but the responses mostly addressed the question "how would you solve this if you had a free choice of problem solving software available?"
I accept that Prolog is a very appropriate programming language for this kind of problem, and there are some fine packages available, e.g. in Python as shown by the top-ranked answer and also standalone. Alas, none of this is helping me "tough it out" in a way as outlined by the book.
The book appears to suggest building a set of dual or perhaps global constraints, and then implementing some of the algorithms mentioned to find a solution. I'm having a lot of trouble coming up with a set of constraints suitable for modelling the problem. I'm studying this on my own so I don't have access to a professor or TA to get me over the hump - this is where I'm asking for your help.
I see little similarity to the examples in the chapter.
I was eager to build dual constraints and started out by creating (the logical equivalent of) 25 variables: nationality1, nationality2, nationality3, ... nationality5, pet1, pet2, pet3, ... pet5, drink1 ... drink5 and so on, where the number was indicative of the house's position.
This is fine for building the unary constraints, e.g.
The Norwegian lives in the first house:
nationality1 = { :norway }.
But most of the constraints are a combination of two such variables through a common house number, e.g.
The Swede has a dog:
nationality[n] = { :sweden } AND pet[n] = { :dog }
where n can range from 1 to 5, obviously. Or stated another way:
nationality1 = { :sweden } AND pet1 = { :dog }
XOR nationality2 = { :sweden } AND pet2 = { :dog }
XOR nationality3 = { :sweden } AND pet3 = { :dog }
XOR nationality4 = { :sweden } AND pet4 = { :dog }
XOR nationality5 = { :sweden } AND pet5 = { :dog }
...which has a decidedly different feel to it than the "list of tuples" advocated by the book:
( X1, X2, X3 = { val1, val2, val3 }, { val4, val5, val6 }, ... )
I'm not looking for a solution per se; I'm looking for a start on how to model this problem in a way that's compatible with the book's approach. Any help appreciated.
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I have a game in which you can score from -40 to +40 on each match.
Users are allowed to play any number of matches.
I want to calculate a total score that implicitly takes into account the number of matches played.
Calculating only the average is not fair.
For example, if Peter plays four games and gets 40 points on each match, he will have the same total
score as Janne who played only one match with 40 points.
Adding up the match scores isn't fair either.
Peter plays 2 games (40 points on each match), total score 80.
Janne plays 8 games (10 points on each match), total score 80.
Is there a (simple) and fair way to calculate the total score?
I have read about the Elo & Glicko system for chess ratings, but both are based upon
a players rating history and the opponents rating.
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Ok I am trying to make something to ask you random multiplication questions. Now it asks the questions fine. Generates the random questions fine. But when it reloads the page the random numbers are different...
how can I fix this?
<?php
$rndnum1 = rand(1, 12);
$rndnum2 = rand(1, 12);
echo "<h3>". $rndnum1 . " x ";
echo $rndnum2 . "</h3>";
if($_SERVER["REQUEST_METHOD"] == "GET") {
$answer=0;
}
else if($_SERVER["REQUEST_METHOD"] == "POST") {
$answer=trim($_POST["answerInput"]);
$check=$rndnum1*$rndnum2;
if($answer==$check) {
echo "Correct!";
}
else {
echo "Wrong!";
}
}
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" >
<table>
<tr>
<td>
First Name:
</td>
<td>
<input type="text" name="answerInput" value="<?php echo $answer; ?>" size="20"/>
</td>
<td>
<?php echo $answerError; ?>
</td>
</tr>
<tr>
<td class="signupTd" colspan="2">
<input type="submit" name="submit" value="Submit"/>
</td>
</tr>
</table>
</form>
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So given x, and power, n, solve for X^n.
There's the easy way that's O(n)...
I can get it down to O(n/2), by doing
numSquares = n/2;
numOnes = n%2;
return (numSquares * x * x + numOnes * x);
Now there's a O(log(n)) solution, does anyone know how to do it? It can be done recursively.
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In a rule system, or any reasoning system that deduces facts via forward-chaining inference rules, how would you prune "unnecessary" branches? I'm not sure what the formal terminology is, but I'm just trying to understand how people are able to limit their train-of-thought when reasoning over problems, whereas all semantic reasoners I've seen appear unable to do this.
For example, in John McCarthy's paper An Example for Natural Language Understanding and the AI Problems It Raises, he describes potential problems in getting a program to intelligently answer questions about a news article in the New York Times. In section 4, "The Need For Nonmonotonic Reasoning", he discusses the use of Occam's Razer to restrict the inclusion of facts when reasoning about the story. The sample story he uses is one about robbers who victimize a furniture store owner.
If a program were asked to form a "minimal completion" of the story in predicate calculus, it might need to include facts not directly mentioned in the original story. However, it would also need some way of knowing when to limit its chain of deduction, so as not to include irrelevant details. For example, it might want to include the exact number of police involved in the case, which the article omits, but it won't want to include the fact that each police officer has a mother.
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If I have a method for calculating the greatest common divisor of two integers as:
public static int GCD(int a, int b)
{
return b == 0 ? a : GCD(b, a % b);
}
What would be the best way to attach that to the System.Math class?
Here are the three ways I have come up with:
public static int GCD(this int a, int b)
{
return b == 0 ? a : b.GCD(a % b);
}
// Lame...
var gcd = a.GCD(b);
and:
public static class RationalMath
{
public static int GCD(int a, int b)
{
return b == 0 ? a : GCD(b, a % b);
}
}
// Lame...
var gcd = RationalMath.GCD(a, b);
and:
public static int GCD(this Type math, int a, int b)
{
return b == 0 ? a : typeof(Math).GCD(b, a % b);
}
// Neat?
var gcd = typeof(Math).GCD(a, b);
The desired syntax is Math.GCD since that is the standard for all mathematical functions.
Any suggestions? What should I do to get the desired syntax?
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Can anyone help me with example on using lapack with latest f#? Or it is not recommended for now?
I searched and only find http://fdatamining.blogspot.com/ but was not able to get FSharp.PowerPack.Math.Providers.dll compiled.
EDIT:
@Yin, Thanks for your blog. On compiling FSharp.PowerPack.Math.Providers.dll from 1.9.7.8 source, Microsoft.FSharp.Compatibility.permutation is used several times and cannot be found. In your blog it is said just to define it explicitly:
type permutation = int –> int.
Alternatively I replace all Microsoft.FSharp.Compatibility.permutation with Microsoft.FSharp.Math.Permutation and got it compiled. Have not test it yet.
Could you please show us the test case for svd bug?
Thanks
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Given a simple data set, I would like to be able to calculate a trending formula given it's a second order polynomial regression.
In fact, it would be great if one could even forecast X periods during calculation (similar to what Excel does).
I'm looking for a portable C/C++ package that's relatively easy to use, and allows it to spit out the "best-fit" (highest R^2 value) curve.
Any suggestions? Thanks!
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How can I write mathematics formula in actionscipt2.0? As following:alt text http://www.freeimagehosting.net/uploads/bc5fee2333.png
Thanks all!
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I have set of points which lies on the image. These set of points form a irregular closed shape. I need to find the area of this shape. Does any body which is the normal algorithm used for calculating the area ? Or is there any support available in libraries such as boost? I am using C++.
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I want to test if a number double x is an integer power of 10. I could perhaps use cmath's log10 and then test if x == (int) x?
edit: Actually, my solution does not work because doubles can be very big, much bigger than int, and also very small, like fractions.
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Heyy Everybody!
I am trying to create a memory management system, so that a user can call myMalloc, a method I created. I have a linked list keeping track of my free memory. My problem is when I am attempting to find the end of a free bit in my linked list. I am attempting to add the size of the memory free in that section (which is in the linked list) to the pointer to the front of the free space, like this.
void *tailEnd = previousPlace->head_ptr + ((previousPlace->size+1)*(sizeof(int));
I was hoping that this would give me a pointer to the end of that segment. However, I keep getting the warning:
"pointer of type 'void*' used in arithmetic"
Is there a better way of doing this? Thanks!
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I am unsure how to put this and my math skills aren't that strong. But here's what I need.
I want to generate a list of all the 16bit integers (0-65535). But everytime I do so I want to seed the algorithm randomly that each time the list starts with a different integer and all the subsequent integers will be generated once but also in random order.
small example (1-5): ...
1, 5, 3, 2, 4
4, 3, 1, 5, 2
2, 1, 4, 5, 3 ...
Any help?
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Does anyone has the formula to convert X,Y,Z,Vx,Vy(cartesian 5D) as well as Azimuth, Elevation(Angular 2D) to Lat Long Alt? Thanks.
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I'm doing simple divisions in c#, and I am a bit puzzled by its intricacies. Here's some code, and in the comments, the result. (btw, I only compile with 1 line not commented, if you say that I have 5 declarations of the same variable)
double result = 2 / 3; //gives 0
double result = Convert.ToDouble(2) / Convert.ToDouble(3); // is good
double result = double.Parse(2) / double.Parse(3); // gives me errors
double result = double.Parse(2 / 3); // gives me errors
double result = Convert.ToDouble(2 / 3); // gives 0
MessageBox.Show(result.ToString());
so if you have a bunch of integers you wanna mess with, you have to convert each one to a double. pretty tedious...
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Does anybody know the mathematics behind an attack on DSA where modulus p has p-1 made up of only small factors. In reality, this would not happen as the key generator would guarantee that this is not so.
There is much information on the web on generating good input paramters for DSA so that it is hard to crack but no information on how you find X if modulus p has p-1 made up of only small factors.
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I am doing this JavaScript math question where it asks me his math question. I do the math, type the answer in the box, and sumbit it. If i am right I move on but I got lost at x.length. I don't know what that means. Here is a example of the problem:
var a= 5+6*4
var b= a / 9
Function (x)
(
if (x.length == b)
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I have two endpoints (xa,ya) and (xb,yb) of two vectors, respectively a and b, originating from a same point (xo, yo). Also, I know that |a|=|b|+s, where s is a constant. I tried to compute the origin (xo, yo) but seem to fail at some point. How to solve this?
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I'm trying to use this formula in JAVA : (-ln(1-L))/L
I'm not sure how to use ln in java.
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I'm using a Segment to Segment closest approach method which will output the closest distance between two segments of length. Each segment corresponds to a sphere object's origin and destination. The speed is simply from one point, to the other.
Closest Approach can succeed even when there won't be a real collision. So, I'm currently using a 10-step method and calculating the distance between 2 spheres as they move along the two segments. So, basically the length of each segment is the object's traverse in the physics step, and the radius is the objects radius. By stepping, I can tell where they collide, and if they collide (Sort of; for the MOST part.)..
I get the feeling that there could be something better. While I sort of believe that the first closest approach call is required, I think that the method immediately following it is a TAD weak. Can anyone help me out? I can illustrate this if needed.
Thanks alot!
(source: yfrog.com)
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HI,
I am trying to use the robust predicates for computational geometry from Jonathan Richard Shewchuk.
I am not a programmer, so I am not even sure of what I am saying, I may be doing some basic mistake.
The point is the predicates should allow for precise aritmthetic with adaptive floating point precision. On my computer: Asus pro31/S (Core Due Centrino Processor) they do not work. The problem may stay in the fact the my computer may use some improvements in the floating point precision taht conflicts with the one used by Shewchuk.
The author says:
/* On some machines, the exact arithmetic routines might be defeated by the */
/* use of internal extended precision floating-point registers. Sometimes */
/* this problem can be fixed by defining certain values to be volatile, */
/* thus forcing them to be stored to memory and rounded off. This isn't */
/* a great solution, though, as it slows the arithmetic down. */
Now what I would like to know is that there is a way, maybe some compiler option, to turn off the internal extended precision floating-point registers.
I really appriaciate your help
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I'm new to SVMs, and I'm trying to use the Python interface to libsvm to classify a sample containing a mean and stddev. However, I'm getting nonsensical results.
Is this task inappropriate for SVMs or is there an error in my use of libsvm? Below is the simple Python script I'm using to test:
#!/usr/bin/env python
# Simple classifier test.
# Adapted from the svm_test.py file included in the standard libsvm distribution.
from collections import defaultdict
from svm import *
# Define our sparse data formatted training and testing sets.
labels = [1,2,3,4]
train = [ # key: 0=mean, 1=stddev
{0:2.5,1:3.5},
{0:5,1:1.2},
{0:7,1:3.3},
{0:10.3,1:0.3},
]
problem = svm_problem(labels, train)
test = [
({0:3, 1:3.11},1),
({0:7.3,1:3.1},3),
({0:7,1:3.3},3),
({0:9.8,1:0.5},4),
]
# Test classifiers.
kernels = [LINEAR, POLY, RBF]
kname = ['linear','polynomial','rbf']
correct = defaultdict(int)
for kn,kt in zip(kname,kernels):
print kt
param = svm_parameter(kernel_type = kt, C=10, probability = 1)
model = svm_model(problem, param)
for test_sample,correct_label in test:
pred_label, pred_probability = model.predict_probability(test_sample)
correct[kn] += pred_label == correct_label
# Show results.
print '-'*80
print 'Accuracy:'
for kn,correct_count in correct.iteritems():
print '\t',kn, '%.6f (%i of %i)' % (correct_count/float(len(test)), correct_count, len(test))
The domain seems fairly simple. I'd expect that if it's trained to know a mean of 2.5 means label 1, then when it sees a mean of 2.4, it should return label 1 as the most likely classification. However, each kernel has an accuracy of 0%. Why is this?
A couple of side notes, is there a way to hide all the verbose training output dumped by libsvm in the terminal? I've searched libsvm's docs and code, but I can't find any way to turn this off.
Also, I had wanted to use simple strings as the keys in my sparse dataset (e.g. {'mean':2.5,'stddev':3.5}). Unfortunately, libsvm only supports integers. I tried using the long integer representation of the string (e.g. 'mean' == 1109110110971110), but libsvm seems to truncate these to normal 32-bit integers. The only workaround I see is to maintain a separate "key" file that maps each string to an integer ('mean'=0, 'stddev'=1). But obviously that'll be a pain since I'll have to maintain and persist a second file along with the serialized classifier. Does anyone see an easier way?
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which part of huge package nltk I must study and use, if I need mark geonames in text?
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We would need to embed mathematical formulas through AsciiMathML into Google Sites pages (internal wiki for a research team). I am stuck with the limitation of Google Sites.
Any idea how to do that?
(ps: I have finally found a poorly practical work-around, but better ideas would still be appreciated)
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I'm working on a sudoko solver (python). my method is using a game tree and explore possible permutations for each set of digits by DFS Algorithm.
in order to analyzing problem, i want to know what is the count of possible valid and invalid sudoko tables?
-> a 9*9 table that have 9 one, 9 two, ... , 9 nine.
(this isn't exact duplicate by this question)
my solution is:
1- First select 9 cells for 1s: (*)
2- and like (1) for other digits (each time, 9 cells will be deleted from remaining available cells):
C(81-9,9) , C(81-9*2,9) .... =
3- finally multiply the result by 9! (permutation of 1s-2s-3s...-9s in (*))
this is not equal to accepted answer of this question but problems are equivalent. what did i do wrong?
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I understand that all math is done as the largest data type required to handle the current values but when you transverse a loop how do you explicitly multiply longs? The following code returns 0, I suspect, because of an overflow.
long result = 0L;
List<Long> temp = (List<Long>) getListOfIntegers();
for (int i = 0; i < temp.size(); i++) {
result *= temp.get(i).longValue();
}
System.out.println(result);
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I intend to develop a J2ME application, that should be able to read words from the English Dictionary. How do I interface to/and store a Dictionary ? Will I have to create the Dictionary myself, by inserting words, or is there a third party Dictionary available with APIs?
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I have a parametric curve, say two vectors of doubles where the parameter is the index, and I have to calculate the angle of the tangent to this curve at any given point (index).
Any suggestion or link about how to do that?
Thanks.
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I'm doing the following in Objective-C and expecting 180 as the output but I'm getting 150. Can anyone explain what I'm doing wrong?
(360 / 100) * 50
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I'm working on coding the Pohlig-Hellman Algorithm but I am having problem understand the steps in the algorithm based on the definition of the algorithm.
Going by the Wiki of the algorithm:
I know the first part 1) is to calculate the prime factor of p-1 - which is fine.
However, I am not sure what I need to do in steps 2) where you calculate the co-efficents:
Let x2 = c0 + c1(2).
125(180/2) = 12590 1 mod (181) so c0 = 0.
125(180/4) = 12545 1 mod (181) so c1 = 0.
Thus, x2 = 0 + 0 = 0.
and 3) put the coefficents together and solve in the chinese remainder theorem.
Can someone help with explaining this in plain english (i) - or pseudocode. I want to code the solution myself obviously but I cannot make any more progress unless i understand the algorithm.
Note: I have done a lot of searching for this and I read S. Pohlig and M. Hellman (1978). "An Improved Algorithm for Computing Logarithms over GF(p) and its Cryptographic Significance but its still not really making sense to me.
Thanks in advance
Update:
how come q(125) stays constant in this example.
Where as in this example is appears like he is calculating a new q each time.
To be more specific I don't understand how the following is computed:
Now divide 7531 by a^c0 to get
7531(a^-2) = 6735 mod p.
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I was working on my advanced calculus homework today and we're doing some iteration methods along the lines of newton's method to find solutions to things like x^2=2. It got me thinking that I could write a function that would take two function pointers, one to the function itself and one to the derivative and automate the process. This wouldn't be too challenging, then I started thinking could I have the user input a function and parse that input (yes I can do that). But can I then dynamically create a pointer to a one-variable function in c++. For instance if x^2+x, can I make a function double function(double x){ return x*x+x;} during run-time. Is this remotely feasible, or is it along the lines of self-modifying code?
Edit:
So I suppose how this could be done if you stored the information in an array and that had a function that evaluated the information stored in this array with a given input. Then you could create a class and initialize the array inside of that class and then use the function from there. Is there a better way?
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I am creating a graphing calculator in Java as a project for my programming class. There are two main components to this calculator: the graph itself, which draws the line(s), and the equation evaluator, which takes in an equation as a String and... well, evaluates it.
To create the line, I create a Path2D.Double instance, and loop through the points on the line. To do this, I calculate as many points as the graph is wide (e.g. if the graph itself is 500px wide, I calculate 500 points), and then scale it to the window of the graph.
Now, this works perfectly for most any line. However, it does not when dealing with singularities.
If, when calculating points, the graph encounters a domain error (such as 1/0), the graph closes the shape in the Path2D.Double instance and starts a new line, so that the line looks mathematically correct. Example:
(source: imagesocket.com)
However, because of the way it scales, sometimes it is rendered correctly, sometimes it isn't. When it isn't, the actual asymptotic line is shown, because within those 500 points, it skipped over x = 2.0 in the equation 1 / (x-2), and only did x = 1.98 and x = 2.04, which are perfectly valid in that equation. Example:
(source: imagesocket.com)
In that case, I increased the window on the left and right one unit each.
My question is: Is there a way to deal with singularities using this method of scaling so that the resulting line looks mathematically correct?
I myself have thought of implementing a binary search-esque method, where, if it finds that it calculates one point, and then the next point is wildly far away from the last point, it searches in between those points for a domain error. I had trouble figuring out how to make it work in practice, however.
Thank you for any help you may give!
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I want to write some games, but I don't have any game development experience. Any books are recommended? Is this necessary to have a good Maths skill when taking about some physical actions? Also, is it complex to do some AI design? thz a lot.
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The following is a survey given to course attendees to assess an instructor at the end of the course.
Communication Skills
1. The instructor communicated course material clearly and accurately.
Yes No
2. The instructor explained course objectives and learning outcomes.
Yes No
3. In the event of not understanding course materials the instructor was available outside of class.
Yes No
4. Was instructor feedback and grading process clear and helpful?
Yes No
5. Do you feel that your oral and written skills have improved while in this course?
Yes No
We would like to summarize each attendees selection based on the choices chosen by him.
If the provided answers were [No, No, Yes, Yes, Yes]. Then we would summarize this as "The instructor was not able to summarize course objectives and learning outcomes clearly, but was available and usually helpful outside of class. The instructor feedback and grading process was clear and helpful and I feel that my oral and written skills have improved because of this course.
Based on the selections chosen by the attendee the summary would be quite different. This leads to many answers based on the choices selected and the number of such questions in the survey. The questions are usually provided by the training organization. How do you come up with a generic solution so that this can be effectively translated into a human readable form. I am looking for tools or libraries (java based), suggestions which will help me create such human readable output. I would like to hide the complexity from the end users as much as possible.
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This may be a little hard to describe since I don't have a sample. I'm trying to find a math function or full 3d function in php or a similar language that can help me with the following effect:
imagine if you were to take a flat sheet or paper and glue it on a glass of water. It wouldn't be flat any more. It would have a curve, and one of its sides might end up being slightly hidden.
Anyone can refer me to a good library or resource on the web where such functions can be found?
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I'm in the process of developing a simple 2d grid based sim game, and have fully functional path finding.
I used the answer found in my previous question as my basis for implementing A* path finding. (Pathfinding 2D Java game?).
To show you really what I'm asking, I need to show you this video screen capture that I made.
I was just testing to see how the person would move to a location and back again, and this was the result...
http://www.screenjelly.com/watch/Bd7d7pObyFo
Different choice of path depending on the direction, an unexpected result. Any ideas?
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Trying to figure out this pseudo code. The following is assumed....
I can only use unsigned and signed integers (or long).
Division returns a real number with no remainder.
MOD returns a real number.
Fractions and decimals are not handled.
INT I = 41828;
INT C = 15;
INT D = 0;
D = (I / 65535) * C;
How would you handle a fraction (or decimal value) in this situation? Is there a way to use negative value to represent the remainder?
In this example I/65535 should be 0.638, however, with the limitations, I get 0 with a MOD of 638. How can I then multiply by C to get the correct answer?
Hope that makes sense.
MOD here would actually return 23707, not 638. (I hope I'm right on that :) )
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I know this is probably a very simple question but how would I do something like
n2 in a programming language?
Is it n * n? Or is there another way?
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I wrote this post
Music and Mathematics, finding the Natural and the Pentatonic scales.
I want to find the best programmatic aproach. A solution could be:
<script>
function getScaleIntervals(c) {
var tot = 0;
var scale = [];
while(tot <= 12){
scale.push(Math.round(tot));
tot += c;
}
return scale;
}
var natural_scale = getScaleIntervals(12/7);
document.write(natural_scale + "
"); // ==> 0, 2, 3, 5, 7, 9, 10, 12
var pentatonic_scale = getScaleIntervals(12/5);
document.write(pentatonic_scale + "
"); // ==> 0, 2, 5, 7, 10, 12
</script>
The resultant intervals starts with D (Re) in 0 so you have D E F G A B C D
This is the Dorian Mode
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I am looking for any free libraries for Named Entity Recognition in c# or any other .net language.
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I am trying to find the linear trend line for a set of data. The set contains pairs of dates (x values) and scores (y values). I am using a version of this code as the basis of my algorithm.
The results I am getting are off by a few orders of magnitude. I assume that there is some problem with round off error or overflow because I am using Date's getTime method which gives you a huge number of milliseconds. Does anyone have a suggestion on how to minimize the errors and compute the correct results?
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I am currently working on a project where I need to generate multiple values (floats or doubles preferably) that follow a power law distribution with a given exponent!
I was advised to use the MathNet.Iridium library to help me. The problem I have is that the documentation is not as explicit as it should be if there is any!
I see multiple distributions that fit the general idea of the power law distribution but I cannot pinpoint a good distribution to use with a certain exponent as a parameter.
Does anybody have more experience in that matter and could give me some hints or advice?
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Basically I am attempting to have an AI agent navigate a world based on given percepts. My issue is handling how the agent moves. Basically, I have created find_action/4 such that we pass in the percepts, action, current cell, and the direction the agent is facing. As it stands the entire code looks like: http://wesnoth.pastebin.com/kdNvzZ6Y
My issue is mainly with lines 102 to 106. Basically, in it's current form the code does not work and the find_action is skipped even when the agent is in fact facing right (I have verified this). This broken code is as follows:
% If we are headed right, take a left turn
find_action([_, _, _, _, _], Action, _, right) :-
retractall(facing(_)),
assert(facing(up)),
Action = turnleft .
However, after some experimentation I have concluded that the following works:
% If we are headed right, take a left turn
find_action([_, _, _, _, _], Action, _, _) :-
facing(right),
retractall(facing(_)),
assert(facing(up)),
Action = turnleft .
I am not entire sure why this is. I've attempted to create several identical find_action's as well, each checking a different direction using the facing(_) format, however swipl does not like this and throws an error.
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I'm given three binary random variables: X, Y, and Z. I'm also given the following:
P(Z | X)
P(Z | Y)
P(X)
P(Y)
I'm then supposed to determine whether or not it is possible to find P(Z | Y, X). I've tried rewriting the solution in the form of Bayes' Theorem and have gotten nowhere. Given that these are boolean random variables, is it possible to rewrite the system in terms of boolean algebra? I understand that the conditionals can be mapped to boolean implications (x -> y, or !x + y), but I'm unsure how this would translate in terms of the overall problem I'm trying to solve.
(yes, this is a homework problem, but here I'm much more interested in how to formally solve this problem than what the solution is...I also figured this question would be entirely too simple for MathOverflow)
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I wish to determine if a Point P(x,y,z) is inside a 2D circle in 3D space defined by its center C (cx, cy, cz), radius R, and normal to the plane the circle lies on N.
I know that a point P lying on a 2D circle in 3D space is defined by:
P = R*cos(t)U + Rsin(t)*( N x U ) + C
where U is a unit vector from the center of the circle to any point on the circle. But given a point Q, how do I know if Q is on or inside the circle? What is the appropriate parameter t to choose? And which coordinates do I compare the point Q to see if they are within the circle?
Thanks.
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Possible Duplicate:
What's wrong with this division?
If you divide 2 / 3, it should return 0.66666666666666667. Instead, I get 0.0 in double value type and 0 in decimal.
My purpose is to divide even (e.g. 2 / 3) and round to 1 always to the nearest.
Any help?
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Ok this is new, Math.Round(1.5) returns 2, i need 1.
How to handle this?
[EDITED] I know its the elementary default way, i need the opposite.
Wrong typing meaning.
Any Suggestions?
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Suppose i have a unsigned integer, call it low and one another call it high such that high>low.
The problem is to find distinct digit set numbers over this range.
For example, suppose low is 1 and high is 20 then the answer is 20, because all the numbers in this range are of distinct digit sets. If suppose low is 1 and high is 21, then the answer is 20, because 12 and 21 have same digit set i.e.1, 2. I am not looking for a bruteforce algo., if anyone has a better solution then a usual bruteforce approach, please tell..
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Let's say I have an array of zeros:
a = numpy.zeros(1000)
I then introduce some repetitive 'events':
a[range(0, 1000, 30)] = 1
Question is, how do I detect the 'signal' there? Because it's far from the ideal signal if I do the 'regular' FFT I don't get a clear indication of where my 'true' signal is:
f = abs(numpy.fft.rfft(a))
Is there a method to detect these repetitions with some degree of certainty? Especially if I have few of those mixed in, for example here:
a[range(0, 1000, 30)] = 1
a[range(0, 1000, 110)] = 1
a[range(0, 1000, 48)] = 1
I'd like to get three 'spikes' on the resulting data...
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Input: two multidimensional (for example dim=8) vectors a and b.
I need to find out the "directed" angle (0-2*Pi, not 0-Pi) between those vectors a and b. And if they are not parallel I need to rotate vector b in plane a,b by "directed" angle L. If they are parallel, plane does not matter, but angle of rotation is still the same L.
For 2d and 3d this is quite easy, but for more dimensions I am lost, I didn't find anything on google, and I prefer using some already proved&tested equations (avoiding errors introduced by my calculations :-D).
Thank you in advance for tips, links, etc.
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Given a integer number and its reresentation in some arbitrary number system. The purpose is to find the base of the number system. For example, number is 10 and representation is 000010, then the base should be 10. Another example: number 21 representation is 0010101 then base is 2. One more example is: number is 6 and representation os 10100 then base is sqrt(2). Does anyone have any idea how to solve such problem?
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I was hoping someone might help with a function that given two parameters:
@param $bytes : total amount in bytes of data consumed
@param $rate : rate per GB, example .22 (for 22 cents)
@returns Total amount owed
Rounded to nearest cent of course. Thanks in advance for any help.
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I have thos piece of code:
Math&&Math.random?Math.floor(Math.random()*10000000000000):Date.getTime();
And as far as i know && is logic operator for AND, so im trying to convert this into PHP and this is where i got:
intval(floor(time()/10800000)%10+(rand()?floor(rand()*10000000000000):time()))
The problem is that i can't understand the first part
Math&&
Can anyone help with this one cause i always get negative result, when i should get positive (probably the logic rand-time is not working in my php example)
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