sub correlation {

  my ($x_ref, $y_ref) = @_;
  
  my $output = "output_test.txt";

  open (OUTPUT_TEST, ">$output");

  print OUTPUT_TEST Dumper ($x_ref, $y_ref);

  #print Dumper length($x_ref);
  #print Dumper length($y_ref);

  my $lfit = Statistics::LineFit->new();
  $lfit->setData($x_ref, $y_ref);
  
  my ($intercept, $slope) = $lfit->coefficients();
  my $rSquared = $lfit->rSquared();
  
  my $hashref = {
		 a => $intercept, 
		 b => $slope, 
		 c => $rSquared
		};

  return $hashref;

}