public static Vec meanVector(DataSet dataSet){
  DenseVector dv=new DenseVector(dataSet.getNumNumericalVars());
  meanVector(dv,dataSet);
  return dv;
}

public static Vec meanVector ( DataSet dataSet ) { DenseVector dv = new DenseVector ( dataSet . getNumNumericalVars ( ) ) ; meanVector ( dv , dataSet ) ; return dv ; }
computes the weighted mean of the given data set .
