sub correlation {

  print "\nWe are in the correlation subroutine\n\n";

  my ($x_ref, $y_ref) = @_;     

  
  
  my @x = @{$x_ref};

  my @y = @{$y_ref}; 


  my $lfit = Statistics::LineFit->new();
  $lfit->setData(@x, @y);
  
  printf "a=%.4f, b=%.4f,  R2=%.4f\n", $lfit->coefficients(), $lfit->rSquared();
  
  
  return  "a=%.4f, b=%.4f, R2=%.4f\n", $lfit->coefficients(), $lfit->rSquared();

}