public static double pdf(double x,double mu,double sigma,double skew){
  x=(x - mu) / sigma;
  if (Math.abs(skew) > 0.) {
    x=-Math.log(1. - skew * x) / skew;
  }
  return MathUtil.SQRTHALF * Math.exp(-.5 * x * x) / sigma / (1 - skew * x);
}

public static double pdf ( double x , double mu , double sigma , double skew ) { x = ( x - mu ) / sigma ; if ( Math . abs ( skew ) > 0. ) { x = - Math . log ( 1. - skew * x ) / skew ; } return MathUtil . SQRTHALF * Math . exp ( - .5 * x * x ) / sigma / ( 1 - skew * x ) ; }
probability density function of the skewed normal distribution .
