Abstract:
A computer system having a visual display which displays data in an interactive split pie chart and permits a user to modify the input parameters of the pie chart to dynamically alter the configuration of the chart. The split pie chart can be split into two or more sections each corresponding to a different time period. Each section is divided into wedges corresponding to different variables and their corresponding values in two different time periods. Finally, the chart itself is geographically placed on a graphic image of a map. An interface between the computer system and a data storage system to transfer data to be transformed into the graphical representation of the pie chart is provided. The user modifies the input parameters of the pie chart through a user interface which translates the modifications into queries to the database storage system to retrieve the appropriate data.

Description:
BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a computer system in which the present invention can be implemented. 
     FIG. 2 is a block diagram illustrating a software subsystem for controlling the operation of the computer system of FIG.  1 . 
     FIG. 3 depicts a block a diagram of the present invention. 
     FIG. 4 depicts a flowchart showing the operation of the present invention. 
     FIG. 5 illustrates the components of the split pie object with its variables and methods. 
     FIG. 6 is a sample table of data to which the present invention could be applied. 
     FIG. 7 is a flowchart depicting the generation of the split pie chart. 
     FIG. 8 is an illustration of a split pie chart of the present invention. 
     FIG. 9 is a sample table with three sets of sales figures. 
     FIG. 10 is a flowchart depicting the additional calculation which occurs when constructing a split pie chart with more than two sets of data points. 
     FIG. 11 is an example of a pie chart split three ways. 
     FIG. 12 depicts a pie chart of the present invention with the geographic variable feature included. 
     FIG. 13 depicts a flowchart of the process of generating a pie chart of with the inclusive geographic variable. 
     FIG. 14 is a flowchart depicting the additional calculation performed to generate a split pie chart with the third dimension of width. 
     FIG. 15 depicts the split pie chart with a third dimension. 
     FIG. 16 depicts a split pie chart where each wedge has its own width. 
     FIG. 17 depicts a flowchart showing the generation of a split pie chart taking into account Stevens&#39; law. 
     FIG. 18 depicts the present invention with tick marks placed around the circumference of the split pie chart. 
     FIG. 19 depicts the present invention with the tick marks placed around the circumference of the larger split in a circle. 
     BACKGROUND OF THE INVENTION 
     In the computer processing field, it is common to store data in a commercial database system and to retrieve such data using a computer system. It is also common to display such information in a variety of ways, each of which is suited for displaying a particular type or quantity of data. Many options are available for presenting data, especially with the advent of word processors, spreadsheets, and graphics software programs for creating tables and graphs. 
     In order to communicate information decisions effectively to users, designers need to understand the tasks in which readers engage when they look at displays. Because the user&#39;s tasks require certain sensory, perceptual and cognitive operations, one has to consider what type of information the user is trying to ascertain in reading the graph. For example, a well-designed line graph makes it easier to discern the slopes of lines, whereas, if the user&#39;s goal is to determine actual values at certain points, differentiating slopes is of little value. 
     There are various factors in making a decision about how to present data. The first factor concerns the amount of data being presented. When presenting a small amount of data, authors should weigh the communicative benefits of tabular or graphical presentation against the reader&#39;s cognitive costs. Generally, in this case, tabular presentation is preferred. However, with a large amount of data, the reader&#39;s use of the data, especially the degree of precision the reader is likely to need, becomes important. If relations are more important than precise values, then the data would probably be best displayed in a graph. Furthermore, readers with a general interest in a topic but no specific interest, may examine a graph to get the main idea. In contrast, readers who have done extensive work on a topic may examine the data in detail. 
     Finally, one must then choose the type of graph to present the information. This decision depends on both the characteristics of on the readers and of independent and dependent variables. Generally, common graphs with which all readers are likely to have experience are used: line graphs, bar graphs, pie charts, and scatter plots. The choice of graph type depends on the readers&#39; informational needs. Either a line graph or a bar graph is used if readers need to determine relative or absolute amounts. A line graph is used if readers need to determine the rate of increase of the dependent (criterion) variable as a function of changes in the independent (predictor) variable. A bar graph is used if readers need to determine the difference between the means of the dependent variable across different levels of the independent variable. A pie chart is used if readers need to determine proportions but not absolute amounts. 
     Another important factor in the design of visual displays is the general relation between physical amount and perceived amount as a power function: perceived amount=a(physical amount) b , known as Stevens&#39; law. When the exponent b=1.0, the increase in perceived amount corresponds to the increase in the physical amount; when b&lt;1.0, the perceived amount increases more rapidly than the physical amount. Because the physical dimensions that display simple linear data extending in either vertical height or horizontal length produce Stevens&#39; law exponents of 1.0, a reader&#39;s perception of the bar graphs and line graphs will accurately correspond to the physical distances shown in the graph. In contrast, the physical dimensions of the area of a rectangle or a circle and the volume of a cube typically produce exponents in Stevens&#39; law of less than 1.0, resulting in an incorrect estimation of the size of indicators. Use of the lightness of shades of gray typically produces an exponent in Stevens&#39; law of greater than 1.0. 
     As per the foregoing, it has always been a goal of the prior art to improve methods of displaying data in a graphically appealing format in order to allow a user to easily ascertain information by viewing the visual display. There is a need in the prior art for a method of displaying data such that relative amounts of data can be clearly visualized with an element of comparison included. 
     It is an object of the present invention to transmit as much information to the user in an organized manner such that the ease with which the user can view and understand the information is maximized. 
     It is an object of the present invention to display data such that a user can not only ascertain relative amounts within a set of data but also the relativity between multiple sets of data. 
     It is a further object of the present invention to provide a means to compare two sets of data corresponding to the same real world parameters with one variable change, such as time period. 
     It is a further object of the present invention to place this comparative graphic display on a graphic image of a map to add the further variable of geographic location. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system and method for the visual display of data in an interactive split pie chart. The pie chart can display multiple sets of dependent variables in relation to at least two other variables, such as time and place. In a preferred embodiment, the split pie chart is split into two sections each corresponding to a different time period, however, any number of sections can be used as is graphically feasible. Each section is divided into wedges corresponding to different variables and their values in the two different time periods. The sizes of the sections are adjusted to demonstrate the relative sizes of the sum total of the two sets of data. Finally, the chart itself is geographically placed on a graphic image of a map. The computer system of the present invention interfaces with a data storage mechanism where the values for the different variables are stored. The user customizes the variables of the pie chart by inputting specific requests into a user interface. The user interface then in turn submits a query to the data storage mechanism for data retrieval. The data storage mechanism returns the values to be used as inputs for the visual display system for the creation of the interactive split pie chart. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description will focus on preferred embodiment of the invention which is operative in a single computer system with an attached data storage mechanism. The present invention, however, is not limited to any particular application or environment. Instead, those skilled in the art will find that the present invention may be advantageously applied to any application or environment where the visual comparison of multiple sets of data with one variable change is desirable. The description of the exemplary embodiment which follows is for the purpose of illustration and not limitation. 
     The invention may be embodied on a computer system such as the system of FIG. 1, which comprises central processor  102 , main memory  104 , input/output controller  106 , keyboard  108 , pointing device  110 , screen display  112 , and data storage mechanism  114 . The data storage mechanism may be any one of a number of database systems such as Microsoft Access, dbase, Oracle, Sybase, etc. The data storage may be a spreadsheet, a relational database, or a multidimensional database. Illustrated in FIG. 2, a computer software system is provided for directing the operation of the computer system. The software system, which is stored in system memory  202 , and on mass storage or disk memory, includes a kernel or operating system  204 , which in this specific embodiment is Windows 95. One or more application programs  206 , such as the application software for the present invention, may be loaded (transferred from disk into main memory) for execution by the system. There is a database management system client  208  running in system memory  202 . The system also includes user interface  210  for receiving user commands and data as input and displaying result data as output. 
     The present invention discloses a means of visual display for a computer system which permits the user to view graphical data in an interactive split pie chart. The display of information on the visual displays can be changed by the user by selecting the appropriate icons in the user interface. While the user may select the view style by keyboard input, in the practice of this invention, the use of a mouse pointer device is preferred. The control and display of a mouse-controlled pointer device, as well as one of more user selectable push buttons, are known as graphic displays, and one skilled in the art can readily generate such graphic displays. In the practice of the present invention, the user may change the data which is displayed in the interactive split pie chart by clicking-and-dragging the mouse pointer device over the appropriate button generated and displayed in the user interface. When the user selects the desired button, the interactive split pie chart is changed to reflect the new data. 
     The system of the present invention is depicted in FIG.  3 . It comprises a user interface  302 , a subsystem for formulating data queries  304 , a first communication means  306  for transmitting the data queries to a database management system  308 , a database storage mechanism  310 , and second communication means  312  for transmitting data from the database storage mechanism to a visual display system  314  and a display  316 . 
     FIG. 4 is a flowchart detailing the operation of the present invention. First, selection  402  of the type of data to be compared takes place, for example, sales for a particular product line. Then, selection  404  of the time periods for which the data will be compared takes place. In the present example, two time periods are used for exemplary purposes. The user can also further make a selection  406  of a particular geographic area for which the comparison is needed. Upon the making of these selections, the computer system formulates  408  queries based on the choices made by the user. In one embodiment, the system generates SQL statements to query a data storage mechanism in which the data is stored. These queries are transmitted  410  to the database management system for retrieval of the data from the data storage mechanism. The data is returned  412  to the visual display system for generation  414  of the split pie chart. The data storage mechanism is preferably either a spreadsheet, a relational database, or a multidimensional database. 
     FIG. 5 illustrates the components of the split pie object  502  used to generate the split pie chart in the preferred embodiment. The LineColor variable  504  specifies the color of chart lines. The LineWidth variable  506  specifies the width of chart lines in pixels. The MaxRadius variable  508  specifies the maximum radius of the chart in pixels. A value of zero indicates that the radius of the chart is unconstrained. The MinRadius variable  510  specifies the minimum radius of the chart in pixels. The OriginOffsetAngle variable  512  specifies the angle from which to begin drawing the chart, in degrees. The RadialOffset variable  514  specifies the angle from which to begin drawing the chart, in radians. The ValuePerUnitArea variable  516  specifies the numerical value represented by a single pixel. The StevensFactor variable  518  specifies the factor by which to scale the values in order to account for the perceptual effect known as Stevens&#39; law. The CrustColor variable  520  specifies the color to use for the outline of the entire split when drawing. The CrustWidth variable  522  specifies the width in pixels of the lines used to draw the outline of the entire split. The TickInterval variable  524  specifies the number of tick marks that should be drawn for each split, and can range from 0 to 12. The TickColor variable  526  specifies the color to use for drawing tick marks. The TicksFollowSplits variable  528  is a true/false value that determines how tick marks are drawn. The AddSlice method  530  adds a data point to the chart. The AutoScale method  532  calculates a value for the ValuePerUnitArea property. The Render method  534  draws the chart. 
     By way of example, FIG. 6 shows a sample table of data which is returned to the visual display system to which the present invention could be applied. In column  602 , there is a list of product lines: cellular phones  604 , home audio/video  606 , computer hardware  608 , computer software  610 , other  612 , and the total  614 . In the second column  616 , are listed the two fiscal years for which the present example applies: 1997 and 1998. In the third column  618 , in cell  620  row  1 , the value denotes the value of cellular phone sales in 1997 and in cell  620 , row  2 , the value denotes the value of cellular phone sales in 1998. FIG. 7 is a flowchart depicting the generation of the pie chart. First, the data is input  702  into the visual display system. The visual display system then separates  704  the different data sets, in this case, the data sets corresponding to the two years. Then, the proportion of each value to the total is calculated  706 . These proportions are converted  708  to fractions of each split, and the wedges are graphically plotted  710 . The visual display system then calculates  712  the relative value of two totals from the two different time periods as a fraction of each other. Finally, the sizes of the two splits are adjusted  714  to reflect this fraction. The present invention calculates the percentage of total sales accounted for by cellular phone sales in 1997 and creates a proportionately sized wedge  802  on the left half  804  of the split pie chart  806  depicted in FIG.  8 . The present invention performs this calculation for each of the product lines for 1997 in order to create the full left split  804  of split pie chart  806 . Then, the present invention calculates the percentage of total sales accounted for by cellular phone sales for 1998 and creates a proportionately sized wedge  808  on the right half  810  of split pie chart  806 . Likewise, the present invention performs this calculation for each of the product lines for 1998 in order to create the full right split  810  of split pie chart  806 . Finally, the present invention calculates the relative size of the total sales from 1998 in comparison to 1997 and increases or decreases the size of the appropriate half in order to reflect that relationship to achieve the goal of the invention, which is to provide a split pie chart for comparison purposes. 
     The present invention is not limited to comparisons of two sets of data points. Similarly, it is possible to compare the sales from multiple different time periods with no limitation on the number of periods. FIG. 9 is a sample table giving an example with three sets of sales figures. The same process described above is applied to scenarios where the user would like to compare multiple sets of data points. FIG. 10 is a flowchart depicting the additional calculation which occurs. First, the data is input  1002  into the visual display system. The system then calculates  1004  the total number of data sets. The pie chart is then split fractionally  1006  into the same number of splits with the same size in degrees of the circle. FIG. 11 is an example of pie chart split three ways. Alternatively, the radial size of the splits can also reflect a comparison. The system can calculate  1008  the relative size of the total size from each year and adjust  1010  the sizes of the splits. The pie chart is then divided  1012  into a number of splits reflecting the number of data sets. Finally, the radial size of the splits can also reflect the relative values of the data set totals. The radial fractions are calculated  1014  from the relative sizes of the totals from the different data sets. The size of the split are adjusted  1016 , and the pie chart is divided  1012  proportionate fractional radial portions. 
     Furthermore, as depicted in FIG. 12, the present invention may also place pie chart  1202  on a computer generated map  1204  such that the data corresponds to the location of the pie chart on the map, based on the previous example. The user may request a plurality of comparisons  1206 ,  1208 ,  1210  simultaneously for different geographic areas. FIG. 13 depicts a flowchart of the process of generating a pie chart with the inclusive geographic variable. When the data is input  1302  into the visual display system, an additional geographic variable of place is also inputted. The system then converts  1304  the physical place into corresponding coordinates on the map by means of a lookup table  1306 , retrieves the coordinates  1308 , and places  1310  the split pie chart appropriately. The present invention will then simultaneously generates multiple split pie charts placed on the computer generated map. In addition, the invention can plot the multiple split pie charts to show relativity between the pie charts themselves. As aforementioned, one can compare the relativity of the two sides of the pie chart based on their sizes. When there are multiple split pie charts in various geographic areas, the total value of the pie charts can be visually compared by the relative sizes of the entire charts in comparison to each other. As can be seen from FIG. 12, pie charts  1206 ,  1208 ,  1210 , are of different total areas. These areas reflect the total value of the sales of each of these regions, as well as the relative value of sales within each region from year to year. 
     In another embodiment, the interactive split pie chart can be given a width, the value of which can correspond to another variable. For example, if a user wanted to compare profitability between the different years, the width variable could be assigned to signify this value. As profitability is not a function of total revenues, the width variable allows the user to get a more accurate sense of the financial performance of the company which for sales are depicted in the table of FIG.  6 . FIG. 14 is a flowchart depicting the additional calculation performed to generate this embodiment of the split pie chart. First, the data is input  1402  to the visual display system. As per the stated example, the system would calculate  1404  the absolute profitability of each year based on that year&#39;s revenues and overhead. The system would then compare  1406  the absolute profitability values from the two time periods and calculate them as fractions of each other. The width dimension of each split would then be adjusted  1408  to reflect the values of these fractions. Therefore, each half of the pie chart can be given its own width to provide another element of comparison. In addition, the profitability of each wedge itself can be calculated  1410 . In the previous example, the profitability of each wedge can be calculated as a percentage value. The multiple profitability values can then be calculated  1412  as fractions of each other in order create wedges of different widths. Each wedge is plotted with a width which reflects its relative profitability compared to other product lines, as well as compared to other years. FIG. 15 depicts the split pie chart described above with the added width dimension. FIG. 16 depicts the split pie chart described above where each wedge has its own width dimension. 
     In yet another embodiment, the interactive split pie chart can be comprised of wedges whose size is adjusted for Stevens&#39; law. Stevens&#39; law embodies the general relation between physical amount and perceived amount which is not necessarily one to one in a graphic image of a circle. The relation is characterized as a power function: perceived amount=a(physical amount) b.  When the exponent b=1.0, the increase in perceived amount corresponds directly to the increase in the physical amount. However, the physical dimensions of the area of a circle typically produce exponents in Stevens&#39; law of less than 1.0. The present invention also provides a means for correcting for this factor. FIG. 17 depicts a flowchart showing the generation of a split pie chart taking into account Stevens&#39; law. The data is input  1702  to the visual display system. The programmer determines  1704  what particular correction factor to use. This factor is then inputted  1706  into the visual display system. The steps of the generation of the pie chart are the same as detailed above except with regard to one step. The wedge sizes are calculated  1708 , and then the sizes are input  1710  into the Stevens&#39; power law to yield the corrected values of the wedge sizes. Before plotting the pie chart itself, the sizes of the splits are adjusted  1712  according to the formula of Stevens&#39; law contingent on the correction factor b which the programmer inputs. Furthermore, the relative sizes of the wedges can also be increased or decreased inclusive of this factor in order to accurately convey the perceived amount to the user. Finally, when placing multiple split pie charts on a map, the total area of the pie charts themselves can be adjusted for Stevens&#39; law. 
     In another embodiment, tick marks can be placed around the circumference of the split pie chart as a visual aid for determining precise quantities. The variables for generating the tick marks are described in FIG. 5, and FIG. 18 depicts the present invention with the tick marks placed right on the circumference of the split pie chart. FIG. 19 depicts the present invention with the tick marks placed around the circumference of the larger split in a true circle.