/usr/share/doc/libplplot11/examples/octave/x22c.m is in octave-plplot 5.9.9-2ubuntu2.
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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 | ## Copyright (C) 2004-2006 Andrew Ross
## Copyright (C) 2004 Rafael Laboissiere
##
## This program is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by the
## Free Software Foundation; either version 2 of the License, or (at your
## option) any later version.
##
## This program 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
## General Public License for more details.
##
## This file is part of plplot_octave.
## It is based on the corresponding demo function of PLplot.
# Simple line plot and multiple windows demo.
1;
function ix22c
## Parse and process command line arguments */
## plparseopts(&argc, argv, PL_PARSE_FULL);
## Initialize plplot */
plinit;
## Set up the data */
## Original case */
circulation;
narr = 6;
fill = 0;
arrow_x = [-0.5 0.5 0.3 0.5 0.3 0.5];
arrow_y = [0.0 0.0 0.2 0.0 -0.2 0.0];
arrow2_x = [-0.5 0.3 0.3 0.5 0.3 0.3];
arrow2_y = [0.0 0.0 0.2 0.0 -0.2 0.0];
## Set arrow style using arrow_x and arrow_y then
## plot using these arrows.
plsvect(arrow_x', arrow_y', fill);
constriction;
## Set arrow style using arrow2_x and arrow2_y then
## plot using these filled arrows. */
fill = 1;
plsvect(arrow2_x', arrow2_y', fill);
constriction;
potential;
## Don't forget to call plend1 to finish off! */
plend1();
endfunction
function circulation
nx = 20;
ny = 20;
dx = 1.0;
dy = 1.0;
xmin = -nx/2*dx;
xmax = nx/2*dx;
ymin = -ny/2*dy;
ymax = ny/2*dy;
xg = [xmin+dx/2:dx:xmax-dx/2]'*ones(1,ny);
yg = ones(nx,1)*[ymin+dy/2:dy:ymax-dy/2];
u = yg;
v = -xg;
## Plot vectors with default arrows
plenv(xmin, xmax, ymin, ymax, 0, 0);
pllab("(x)", "(y)", "#frPLplot Example 22 - circulation");
plcol0(2);
plvect2(u,v,0.0,xg,yg);
plcol0(1);
end
## Vector plot of flow through a constricted pipe
function constriction
nx = 20;
ny = 20;
dx = 1.0;
dy = 1.0;
xmin = -nx/2*dx;
xmax = nx/2*dx;
ymin = -ny/2*dy;
ymax = ny/2*dy;
Q = 2.0;
xg = [xmin+dx/2:dx:xmax-dx/2]'*ones(1,ny);
yg = ones(nx,1)*[ymin+dy/2:dy:ymax-dy/2];
b = ymax/4.0.*(3-cos(pi*xg/xmax));
dbdx = ymax/4.0.*sin(pi*xg/xmax).*yg./b;
u = Q*ymax./b.*(abs(yg)<b);
v = dbdx.*u.*(abs(yg)<b);
plenv(xmin, xmax, ymin, ymax, 0, 0);
pllab("(x)", "(y)", "#frPLplot Example 22 - constriction");
plcol0(2);
plvect2(u,v,-0.5,xg,yg);
plcol0(1);
end
## Vector plot of the gradient of a shielded potential (see example 9)
function potential
nper = 100;
nlevel = 10;
nr = 20;
ntheta = 20;
## 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.
rmax = nr;
eps = 2.;
q1 = 1.;
d1 = rmax/4.;
q1i = - q1*rmax/d1;
d1i = rmax^2/d1;
q2 = -1.;
d2 = rmax/4.;
q2i = - q2*rmax/d2;
d2i = rmax^2/d2;
r = [0.5:1:nr-0.5];
dtheta = 2*pi/(ntheta-1);
theta = [dtheta/2:dtheta:2*pi+dtheta/2];
x = r'*cos(theta);
y = r'*sin(theta);
div1 = sqrt((x-d1).^2 + (y-d1).^2 + eps^2);
div1i = sqrt((x-d1i).^2 + (y-d1i).^2 + eps^2);
div2 = sqrt((x-d2).^2 + (y+d2).^2 + eps^2);
div2i = sqrt((x-d2i).^2 + (y+d2i).^2 + eps^2);
z = q1*div1.^-1 + q1i*div1i.^-1 + q2*div2.^-1 + q2i*div2i.^-1;
u = -q1*(x-d1)./div1.^3 - q1i*(x-d1i)./div1i.^3 - q2*(x-d2)./div2.^3 - q2i*(x-d2i)./div2i.^3;
v = -q1*(y-d1)./div1.^3 - q1i*(y-d1i)./div1i.^3 - q2*(y+d2)./div2.^3 - q2i*(y+d2i)./div2i.^3;
xmin = min(min(x));
xmax = max(max(x));
ymin = min(min(y));
ymax = max(max(y));
zmin = min(min(z));
zmax = max(max(z));
plenv(xmin, xmax, ymin, ymax, 0, 0);
pllab("(x)", "(y)", "#frPLplot Example 22 - potential gradient vector plot");
## Plot contours of the potential
dz = (zmax-zmin)/nlevel;
clevel = [zmin+dz/2:dz:zmax-dz/2];
plcol0(3);
pllsty(2);
plcont2(z,1,nr,1,ntheta,clevel',x,y);
pllsty(1);
plcol0(1);
## Plot the vectors of the gradient of the potential
plcol0(2);
plvect2(u,v,25.0,x,y);
plcol0(1);
## Plot the perimeter of the cylinder
theta = [0:2*pi/(nper-1):2*pi];
px = rmax*cos(theta);
py = rmax*sin(theta);
plline(px',py');
end
ix22c
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