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Dirichlet Distribution (in Wolfram Alpha)

Posted 10 years ago

Hello,

First: I'm new here and don't know exactly how the groups work, if there is a group for this, please tell me the right one.

I want to use this:

http://reference.wolfram.com/language/ref/DirichletDistribution.html

But the examples don't work.

Also, if they would work, I would like to have a plot of a given dimension and I want to calculate the value of a certain coordinate for a special dimension.

Like DirichletDistribution[alpha1=20, alpha2=30, alpha3=50, dimension=0, x=0.2]

At x=0.2 I suspect the highest value in dimension 0.

Is there a way to make this possible?

POSTED BY: Soer Klett
4 Replies

When I asked about many-argument Dirichlet Distribution, I was told,

Neither multivariate distributions nor distributions with a variable number of parameters is supported in Wolfram|Alpha at the moment. Support for both are future goals.

I do not know of a Wolfram|Alpha language reference. It would be changing frequently.

If you have a question about what Wolfram|Alpha can handle, I suggest using the feedback slot at the bottom of Wolfram|Alpha pages (the slot enlarges when you type into it) or send email to info@wolframalpha.com.

POSTED BY: Bruce Miller

"But the examples don't work." - in the web browser? in WolframAlpha.com? in Mathematica?

Since Wolfram|Alpha is one of the groups for this post, I will assume you mean WolframAlpha.com.

I typed $DirichletDistribution$ into Alpha and it returned a description that had only two parameters. I found that I can enter DirichletDistribution with two arguments into Alpha and it gives an output. It might not know about DirichletDistribution with many arguments.

enter image description here

POSTED BY: Bruce Miller
Posted 10 years ago

Thank you very much, looks like I confused the documentations. I used Ubuntu, Chromiuma and the wolframalpha- web-interface. I thought the things in the documentation would work there too. Is there a way to see the wolframalpha web documentation, only? Or should I just try the examples, and if they don't work test it in the offline version?

POSTED BY: Soer Klett

When you say that the examples don't work, which ones don't work? When I go to the Documentation Center for DirichletDistribution the examples all seem to work as advertised.

Note that, for example,

DirichletDistribution[{1, 3, 2}]

is a symbolic representation of the DirichletDistribution at those values of its parameters. You need to then put it into, for example, PDF, to get its value at a particular point. So,

PDF[DirichletDistribution[{1, 3, 2}], {x, y}]

returns

Piecewise[{{60*(1 - x - y)*y^2, x > 0 && y > 0 && 1 - x - y > 0}}, 0]

And so on....

Read http://reference.wolfram.com/language/tutorial/ContinuousDistributions.html to get some more background on how to work with probability distributions in Mathematica.

POSTED BY: David Reiss
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