#
# Compare to fig 5, of Hogg, D. W., "Distance measures in cosmology",
# astro-ph/9905116
#
use strict;
use PDL;
use blib;
# cosmologies - h0 is irrelevant here
my $a = new Astro::Cosmology { matter => 1.0, lambda => 0.0, h0 => 0.0 };
my $b = new Astro::Cosmology { matter => 0.05, lambda => 0.0, h0 => 0.0 };
my $c = new Astro::Cosmology { matter => 0.2, lambda => 0.8, h0 => 0.0 };
# z range
my $z = 0.1 * sequence(51);
# calculate the normalised comoving volume element
# - ie the differential comoving volume element
my $d_a = $a->dcomov_vol( $z );
my $d_b = $b->dcomov_vol( $z );
my $d_c = $c->dcomov_vol( $z );
# plot the graph
my $win = PDL::Graphics::PGPLOT::Window->new();
$win->env( 0, 5, 0, 1.1 );
$win->label_axes( "redshift z",
"comoving volume element [1/D\\dH\\u]\\u3\\d dV\\dc\\u/dz/d\\gW",
"Fig 5 of Hogg, D.W. astro-ph/9905116" );
$win->hold;
$win->line( $z, $d_a, { LINESTYLE => 'solid' } );
$win->line( $z, $d_b, { LINESTYLE => 'dotted' } );
$win->line( $z, $d_c, { LINESTYLE => 'dashed' } );
$win->release;
$win->close;
## End of the test
exit;