/usr/share/doc/libplplot12/examples/perl/x22.pl is in libplplot-dev 5.10.0+dfsg-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 | #! /usr/bin/env perl
#
# Demo x22 for the PLplot PDL binding
#
# Simple vector plot example
#
# Copyright (C) 2004 Rafael Laboissiere
#
# This file is part of PLplot.
#
# PLplot is free software; you can redistribute it and/or modify
# it under the terms of the GNU Library General Public License as published
# by the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# PLplot is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Library General Public License for more details.
#
# You should have received a copy of the GNU Library General Public License
# along with PLplot; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
# SYNC: x22c.c 1.8
use PDL;
use PDL::Graphics::PLplot;
use Math::Trig qw [pi];
use constant nx => 20;
use constant ny => 20;
use constant nr => 20;
use constant ntheta => 20;
use constant nper => 100;
use constant nlevel => 10;
# Pairs of points making the line segments used to plot the user defined
# arrow
my $arrow_x = pdl [-0.5, 0.5, 0.3, 0.5, 0.3, 0.5];
my $arrow_y = pdl [0.0, 0.0, 0.2, 0.0, -0.2, 0.0];
my $arrow2_x = pdl [-0.5, 0.3, 0.3, 0.5, 0.3, 0.3];
my $arrow2_y = pdl [0.0, 0.0, 0.2, 0.0, -0.2, 0.0];
#
# Vector plot of the circulation about the origin
#
sub circulation {
my $dx = 1.0;
my $dy = 1.0;
my $nx = nx;
my $ny = ny;
my $xmin = -$nx/2*$dx;
my $xmax = $nx/2*$dx;
my $ymin = -$ny/2*$dy;
my $ymax = $ny/2*$dy;
my $x = ((sequence($nx)-int($nx/2)+0.5)*$dx)->dummy(1,$ny);
my $y = ((sequence($ny)-int($ny/2)+0.5)*$dy)->dummy(0,$nx);
# Create data - circulation around the origin.
my $cgrid2 = plAlloc2dGrid($x, $y);
my $u = $y;
my $v = -$x;
# Plot vectors with default arrows
plenv($xmin, $xmax, $ymin, $ymax, 0, 0);
pllab("(x)", "(y)", "#frPLplot Example 22 - circulation");
plcol0(2);
plvect($u,$v,0.0,\&pltr2,$cgrid2);
plcol0(1);
}
#
# Vector plot of flow through a constricted pipe
#
sub constriction {
my $nx = nx;
my $ny = ny;
my $dx = 1.0;
my $dy = 1.0;
my $xmin = -$nx/2*$dx;
my $xmax = $nx/2*$dx;
my $ymin = -$ny/2*$dy;
my $ymax = $ny/2*$dy;
my $x = ((sequence($nx)-int($nx/2)+0.5)*$dx)->dummy(1,$ny);
my $y = ((sequence($ny)-int($ny/2)+0.5)*$dy)->dummy(0,$nx);
my $cgrid2 = plAlloc2dGrid($x, $y);
my $u;
my $v;
my $Q = 2.0;
my $b = $ymax/4.0*(3-cos(pi*$x/$xmax));
my $dbdx = $ymax/4.0*sin(pi*$x/$xmax)*$y/$b;
$u = $Q*4*$ymax/$b;
$v = $dbdx*$u;
$u->where(abs($y)>=$b) .= 0;
$v->where(abs($y)>=$b) .= 0;
plenv($xmin, $xmax, $ymin, $ymax, 0, 0);
pllab("(x)", "(y)", "#frPLplot Example 22 - constriction");
plcol0(2);
plvect($u,$v,-0.5,\&pltr2,$cgrid2);
plcol0(1);
}
sub f2mnmx {
$f = shift;
my $fmin = min ($f);
my $fmax = max ($f);
return ($fmin, $fmax);
}
# Vector plot of the gradient of a shielded potential (see example 9)
sub potential {
# Potential inside a conducting cylinder (or sphere) by method of images.
# Charge 1 is placed at (d1, d1), with image charge at (d2, d2).
# Charge 2 is placed at (d1, -d1), with image charge at (d2, -d2).
# Also put in smoothing term at small distances.
my $rmax = nr;
my $eps = 2;
my $q1 = 1;
my $d1 = $rmax / 4;
my $q1i = - $q1 * $rmax / $d1;
my $d1i = $rmax * $rmax / $d1;
my $q2 = -1;
my $d2 = $rmax / 4;
my $q2i = - $q2 * $rmax / $d2;
my $d2i = $rmax * $rmax / $d2;
my $r = (0.5 + sequence (nr))->dummy (1, ntheta);
my $theta = (2 * pi / (ntheta - 1) *
(0.5 + sequence (ntheta)))->dummy (0, nr);
my $x = $r * cos ($theta);
my $y = $r * sin ($theta);
my $cgrid2 = plAlloc2dGrid ($x, $y);
my $div1 = sqrt (($x - $d1) ** 2 + ($y - $d1) ** 2 + $eps * $eps);
my $div1i = sqrt (($x - $d1i) ** 2 + ($y - $d1i) ** 2 + $eps * $eps);
my $div2 = sqrt (($x - $d2) ** 2 + ($y + $d2) ** 2 + $eps * $eps);
my $div2i = sqrt (($x - $d2i) ** 2 + ($y + $d2i) ** 2 + $eps * $eps);
my $z = $q1 / $div1 + $q1i / $div1i + $q2 / $div2 + $q2i / $div2i;
my $u = -$q1 * ($x - $d1) / ($div1**3) - $q1i * ($x - $d1i) / ($div1i ** 3)
-$q2 * ($x - $d2) / ($div2**3) - $q2i * ($x - $d2i) / ($div2i ** 3);
my $v = -$q1 * ($y - $d1) / ($div1**3) - $q1i * ($y - $d1i) / ($div1i ** 3)
-$q2 * ($y + $d2) / ($div2**3) - $q2i * ($y + $d2i) / ($div2i ** 3);
my ($xmin, $xmax) = f2mnmx ($x);
my ($ymin, $ymax) = f2mnmx ($y);
my ($zmin, $zmax) = f2mnmx ($z);
plenv ($xmin, $xmax, $ymin, $ymax, 0, 0);
pllab ("(x)", "(y)",
"#frPLplot Example 22 - potential gradient vector plot");
# Plot contours of the potential
my $dz = ($zmax - $zmin) / nlevel;
my $clevel = $zmin + (sequence (nlevel) + 0.5) * $dz;
plcol0 (3);
pllsty (2);
plcont ($z, 1, nr, 1, ntheta, $clevel, \&pltr2, $cgrid2);
pllsty (1);
plcol0 (1);
# Plot the vectors of the gradient of the potential
plcol0 (2);
plvect ($u, $v, 25.0, \&pltr2, $cgrid2);
plcol0 (1);
# Plot the perimeter of the cylinder
$theta = (2 * pi / (nper - 1)) * sequence (nper);
my $px = $rmax * cos ($theta);
my $py = $rmax * sin ($theta);
plline ($px , $py);
}
#--------------------------------------------------------------------------
# main
#
# Generates several simple vector plots.
#--------------------------------------------------------------------------
# Parse and process command line arguments
plParseOpts (\@ARGV, PL_PARSE_SKIP | PL_PARSE_NOPROGRAM);
# Initialize plplot
plinit ();
circulation();
# Set arrow style using arrow_x and arrow_y then
# plot using these arrows.
my $fill = 0;
plsvect($arrow_x, $arrow_y, $fill);
constriction();
# Set arrow style using arrow2_x and arrow2_y then
# plot using these filled arrows.
my $fill = 1;
plsvect($arrow2_x, $arrow2_y, $fill);
constriction();
# Example of polar plot
potential ();
plend ();
|