public static double nextWeibull(double alpha,double beta,RandomEngine randomGenerator){
  return Math.pow(beta * (-Math.log(1.0 - randomGenerator.raw())),1.0 / alpha);
}

public static double nextWeibull ( double alpha , double beta , RandomEngine randomGenerator ) { return Math . pow ( beta * ( - Math . log ( 1.0 - randomGenerator . raw ( ) ) ) , 1.0 / alpha ) ; }
returns a weibull distributed random number . polar method . see simulation , modelling & analysis by law & kelton , pp259
