question: public static double logPdf ( double x , double m , double sd ) { double a = 1.0 / ( Math . sqrt ( 2.0 * Math . PI ) * sd ) ; double b = - ( x - m ) * ( x - m ) / ( 2.0 * sd * sd ) ; return Math . log ( a ) + b ; }
target:  the natural log of the probability density function of the distribution