question: protected static double regularizedIncBetaCF ( double alpha , double beta , double x ) { final double FPMIN = Double . MIN_VALUE / NUM_PRECISION ; double qab = alpha + beta ; double qap = alpha + 1.0 ; double qam = alpha - 1.0 ; double c = 1.0 ; double d = 1.0 - qab * x / qap ; if ( Math . abs ( d ) < FPMIN ) { d = FPMIN ; } d = 1.0 / d ; double h = d ; for ( int m = 1 ; m < 10000 ; m ++ ) { int m2 = 2 * m ; double aa = m * ( beta - m ) * x / ( ( qam + m2 ) * ( alpha + m2 ) ) ; d = 1.0 + aa * d ; if ( Math . abs ( d ) < FPMIN ) { d = FPMIN ; } c = 1.0 + aa / c ; if ( Math . abs ( c ) < FPMIN ) { c = FPMIN ; } d = 1.0 / d ; h *= d * c ; aa = - ( alpha + m ) * ( qab + m ) * x / ( ( alpha + m2 ) * ( qap + m2 ) ) ; d = 1.0 + aa * d ; if ( Math . abs ( d ) < FPMIN ) { d = FPMIN ; } c = 1.0 + aa / c ; if ( Math . abs ( c ) < FPMIN ) { c = FPMIN ; } d = 1.0 / d ; double del = d * c ; h *= del ; if ( Math . abs ( del - 1.0 ) <= NUM_PRECISION ) { break ; } } return h ; }
target:  Returns the regularized incomplete beta function I_x(a, b) Includes the continued fraction way of computing, based on the book "Numerical Recipes".