private double[][] xPrime(int t){
  double[][] x=new double[1][getNumLags() * numVars];
  for (int i=0; i < getNumLags(); i++) {
    double[][] yPrime=yPrime(t - i - 1);
    System.arraycopy(yPrime[0],0,x[0],i * numVars,numVars);
  }
  return x;
}

private double [ ] [ ] xPrime ( int t ) { double [ ] [ ] x = new double [ 1 ] [ getNumLags ( ) * numVars ] ; for ( int i = 0 ; i < getNumLags ( ) ; i ++ ) { double [ ] [ ] yPrime = yPrime ( t - i - 1 ) ; System . arraycopy ( yPrime [ 0 ] , 0 , x [ 0 ] , i * numVars , numVars ) ; } return x ; }
constructs the x ( t ) vector .
