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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | 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); |