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

  return  "a=%.4f, b=%.4f,  R2=%.4f\n", $lfit->coefficients(), $lfit->rSquared();

}