BetaIaInv(p, x, b)
Computes the inverse of the incomplete beta function, BetaI(p, a, b) with respect to «a». In other words, BetaIaInv returns a value such that
BetaI(p, BetaIaInv(p, x, b), b) is equal to «x».
Note that this is similar to the BetaIInv(y, a, b) function, except that BetaIInv inverts BetaI with respect to the first parameter, «p», whereas BetaIaInv inverts it relative to the second parameter, «a».
CumNegativeBinomInv(u, r, p) + 1 = BetaIaInv(p, 1 - u, r)
The function was introduced in Analytica 4.5.