returns the integral from zero to x of the gamma probability density function . alpha - x beta | alpha-1 - beta t y = --------- | t e dt - | | alpha - 0 the incomplete gamma integral is used , according to the relation y = gamma.incompletegamma alpha , betax . see http://en.wikipedia.org/wiki/gamma_distribution#probability_density_function concode_field_sep Normal UNIT_NORMAL concode_field_sep double normal concode_elem_sep double normal concode_elem_sep double negativeBinomial concode_elem_sep double poisson concode_elem_sep double beta
double function ( double arg0 , double arg1 , double arg2 ) { if ( arg2 < 0.0 ) { return 0.0 ; } return Gamma . incompleteGamma ( arg0 , arg1 * arg2 ) ; }