Talk:Dirichlet process

message: The main page explains how to create the initial assignment of cluster members (for example using the chinese restaurant process) but leaves out a clear description of how to update the cluster assignments to obtain meaningful clusters. The assignment algorithms assign members to clusters initially without regard to the members' properties/features. From my discussions here (http://metaoptimize.com/qa/questions/10731/dirichlet-process-basic-intuition) it was explained that there is a step (using MCMC/GIBBS) which moves the documents around until the clusters are stable that is key to understanding how DP produces non-random results. Clearly, a detailed explanation of MCMC (and the alternatives) belongs in their own wikipages but the DP page needs to make it clear that this optimization step is key (without it, DP seems like bad magic).  — Preceding unsigned comment added by Swframe (talk • contribs) 18:34, 3 August 2012 (UTC)
replies: text: The reason is that the Dirichlet process has no optimisation step. You're thinking about the Dirichlet process embedded in a Bayesian optimisation problem, but this article is about the Dirichlet process generally.--mcld (talk) 14:07, 30 July 2013 (UTC)
thread_title:  Missing clear description of the optimization step 

message: The \delta in the formula is undefined. Anyone know what it is? Took 04:49, 31 October 2007 (UTC)
thread_title:  Stick-breaking Construction 

message: What exactly is the relationship between the chinese restaurant process and the Dirichlet process?  The article does not make it clear. Robinh (talk) 07:51, 1 August 2008 (UTC)
thread_title: Chinese restaurant process

message: The text with the CRP visualization states: "Additionally, a customer opens a new table with a probability proportional to the scaling parameter \alpha." However, the visualization with \alpha = 1/2 shows the new table as already being present with half 
a customer sitting at it. That's very difficult restaurant to imagine and doesn't help the metaphor in any way. For example rather than 9 customers present it shows 9.5 total customers. Also if alpha = 3, and 9 customers entered the restaurant are there in total 12 customers? Someone should render the video again. Anne van Rossum (talk) 19:53, 21 June 2017 (UTC)
thread_title:  Half a customer 

message: "The smaller α is, more of the stick will be left for subsequent values (on average)."
Shouldn't it be "less of the stick will be left..."? Took (talk) 19:34, 31 March 2009 (UTC)
replies: text: Yes I think you're right, will change the article --mcld (talk) 11:08, 12 March 2010 (UTC)

text: I see now that i is just the number of total counts given a set of 1-of-K random variables and equal to N above. Sorry for the confusion, it just looks like i is an arbitrary index and the denominator is a function of that index.Bamayer (talk) 23:11, 20 November 2012 (UTC)
thread_title:  Stick-breaking Construction possible error 

message: The phrase
:: Given a set S equipped with a suitable \sigma-algebra,
does nothing to inform the lay reader that mathematics is what the article is about.  It is a terrible phrase to use as the beginning of a Wikipedia article. Michael Hardy (talk) 05:47, 22 May 2009 (UTC)
replies: text: I know this is a bit of an exercise in archaeology here, but I just wanted to mention that the 1973 paper by Thomas Ferguson introducing the Dirichlet process uses a single parameter, so it's a stretch to say it's inconsistent with all other literature. "Definition 1" from that paper says "We say P is a Dirichlet process [...] with parameter α [...]" where α is a "non-null finite measure." https://projecteuclid.org/euclid.aos/1176342360. The Blackwell & MacQueen paper motivating the "Polya urn scheme" section of the article uses a single parameter too, and so does a 1994 paper by Sethuraman I have sitting in front of me, which makes obvious why one parameter is equivalent: "Let α be a non-zero finite measure on (X,\mathcal{B}). Let β(B) = α(B)/α(X) be the normalized probability measure arising from α." 2604:6000:1402:8245:3BE4:7366:E64E:B0D9 (talk) 00:40, 26 May 2019 (UTC)
thread_title:  Context 

message: It would be great if there is a section dedicated to inference and a section with applications. But preferably not in the way as the monster article https://en.wikipedia.org/wiki/Dirichlet-multinomial_distribution. 145.94.110.25 (talk) 11:06, 12 November 2013 (UTC)
thread_title:  Inference and applications sections 

message: This is super-important. I don't know how to say Dirichlet and I don't want to sound stupid...  — Preceding unsigned comment added by 129.6.220.243 (talk) 14:31, 4 March 2016 (UTC)
thread_title:  How do you pronounce Dirichlet? 

message: What am I missing? The introduction describes drawing from a Dirichlet:
# Draw X_{1} from the distribution H.
# For n>1: 
:::: a)  With probability  \frac{\alpha}{\alpha+n-1}  draw X_{n} from H.
:::: b)  With probability  \frac{n_{x}}{\alpha+n-1}  set X_{n}=x, where n_{x} is the number of previous observations X_{j}, j<n, such that X_{j}=x. 
How does  n_x ever increase beyond 0? If X_1 comes from H then X_2 must also come from H since n_x is still 0 at n = 2. Similarly for X_3 and so on. Why isn't the probability of setting X_n = x just 1-\frac{\alpha}{\alpha+n-1} for any n? Don't the probabilities of drawing X_n from H and setting X_n = x have to sum to 1 for any value of n? What did I miss? Chafe66 (talk) 18:34, 26 April 2016 (UTC)
replies: text: I'm confused about your confusion; e.g. if X_1 = x then at step 2 n_x = 1 and X_2 = x with probability \frac{1}{\alpha+n-1} Victor veitch (talk) 20:08, 27 April 2016 (UTC)
replies: text:  Oh--I didn't see that the first draw is x  by definition basically. I thought the implication was that the value x  was not from the distn  H , which of course would make no sense whatsoever. In the words of Gilda Radner "nevermind." ;) Chafe66 (talk) 17:37, 6 May 2016 (UTC)
thread_title:  Introduction 

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thread_title:  External links modified