public static double logcdf(double val,double loc,double scale,double shape){
  val=(val - loc) / scale;
  return Math.log1p(Math.exp(-val)) * -shape;
}

public static double logcdf ( double val , double loc , double scale , double shape ) { val = ( val - loc ) / scale ; return Math . log1p ( Math . exp ( - val ) ) * - shape ; }
log cumulative density function . todo : untested .
