Advanced math functions for AS3

admin — Sat, 21 Feb 2009 22:29:14 +0000

Did you ever need to sample from a Dirichlet distribution in Actionscript 3.0? What about computing a value of the Gamma function? Probably not In case you did, I wrote a class with a few math methods:

a function to sample from multinomial distributions; this is useful if you need to choose randomly from a set of elements, each with a different probability;
functions to draw samples from the Dirichlet and Gamma distribution;
the Gamma function
a factorial function that works even for large values (using the identity n! = Gamma(n+1))
other utility functions, e.g. to compute mean and variance of an array, or add two arrays together

You can download the AdvancedMath class here, it includes AsUnit tests.

This is an example of how to use the AdvancedMath class to simulate a rigged dice: the code below throws the dice 1000 times, and keeps a count of how many times one gets the different faces.

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import com.masterbaboon.AdvancedMath;

// probability of the faces; 6 is about twice more likely to appear
var p:Array = [0.14, 0.14, 0.14, 0.14, 0.14, 0.3];

// count the number of times a face appears
var count:Array = AdvancedMath.zeros(6);

// throw dice 1000 times
var face:int;
for (var i:int = 0; i < 1000; i++) {
face = AdvancedMath.sampleMultinomial(p);
count[face]++;
}

// show how many times we got which face
trace(count);

Master Baboon » AdvancedMath

Advanced math functions for AS3