stats_cdf_beta

Additional Notes, taken from source. WHICH --> Integer indicating which of the next four argument       values is to be calculated from the others.     Legal range: 1..4     iwhich = 1 : Calculate P and Q from X,Y,A and B     iwhich = 2 : Calculate X and Y from P,Q,A and B     iwhich = 3 : Calculate A from P,Q,X,Y and B     iwhich = 4 : Calculate B from P,Q,X,Y and A          P <--> The integral from 0 to X of the chi-square     distribution.     Input range: [0, 1].          Q <--> 1-P.     Input range: [0, 1].     P + Q = 1.0.          X <--> Upper limit of integration of beta density.     Input range: [0,1].     Search range: [0,1]          Y <--> 1-X.     Input range: [0,1].     Search range: [0,1]     X + Y = 1.0.          A <--> The first parameter of the beta density.     Input range: (0, +infinity).     Search range: [1D-100,1D100]          B <--> The second parameter of the beta density.     Input range: (0, +infinity).     Search range: [1D-100,1D100]

Decided to dive into the source code and provide a simple explanation:Parameters:int $which - Select which parameter to use in the CDF Binomial calculation, based on what the prior 3 parameters are.where $which is 4:$arg1 = p$arg2 = sn$arg3 = xnreturns pr$which = 3$arg1 = p$arg2 = sn$arg3 = prreturns xn$which = 2$arg1 = p$arg2 = xn$arg3 = prreturns sn$which = 1$arg1 = sn$arg2 = xn$arg3 = prreturns p