A set of functions to calculate the probability of intersection between sets being a chance event in a hypergeometric distribution

hypergeometric_probability.js

function GetBinCoeff(N, K) {
    // http://stackoverflow.com/questions/14556266/how-to-calculate-combination-of-large-numbers
    if ( K > N) {
        return 0;
    }
    else {
       var r = 1;
       var d;
       for (d = 1; d <= K; d++)
       {
          r *= N--;
          r /= d;
       }
       return r;
    }
}

function hypergeometric(N, K, n, k) {
	// https://www.biostars.org/p/15548/
	// http://en.wikipedia.org/wiki/Hypergeometric_distribution
    return GetBinCoeff(K, k) * GetBinCoeff(N-K, n-k) / GetBinCoeff(N, n);
}