#!/usr/bin/perl -w
use strict;
use Chart::Gnuplot;
# Create the chart object
my $chart = Chart::Gnuplot->new(
output => "plot3d_8.png",
title => "3D surface with contour",
contour => "base",
);
# Data set object
my $dataSet = Chart::Gnuplot::DataSet->new(
func => "-(x**2 + y**2)",
);
# Plot the graph
$chart->plot3d($dataSet);