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// $Id: x22.java 12832 2013-12-09 14:39:59Z andrewross $
// Simple vector plot example
//--------------------------------------------------------------------------
//
//--------------------------------------------------------------------------
// Copyright (C) 2004 Andrew Ross
//
// 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; version 2 of the License.
//
// 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
//--------------------------------------------------------------------------
//
//--------------------------------------------------------------------------
// Implementation of PLplot example 22 in Java.
//--------------------------------------------------------------------------
package plplot.examples;
import plplot.core.*;
import static plplot.core.plplotjavacConstants.*;
import java.lang.Math;
class Transform implements PLCallbackCT {
public void coordTransform( double x, double y, double[] xt, double[] yt, Object data )
{
double xmax;
xmax = 10.0;
xt[0] = x;
yt[0] = y / 4.0 * ( 3 - Math.cos( Math.PI * x / xmax ) );
}
}
class x22 {
double MIN( double x, double y ) { return ( x < y ? x : y ); }
double MAX( double x, double y ) { return ( x > y ? x : y ); }
PLStream pls = new PLStream();
double[][] u = null;
double[][] v = null;
double[][] xg = null;
double[][] yg = null;
int nx, ny, nc, nseg;
// Vector plot of the circulation about the origin
void circulation()
{
int i, j;
double dx, dy, x, y;
double xmin, xmax, ymin, ymax;
dx = 1.0;
dy = 1.0;
xmin = -nx / 2 * dx;
xmax = nx / 2 * dx;
ymin = -ny / 2 * dy;
ymax = ny / 2 * dy;
// Create data - cirulation around the origin.
for ( i = 0; i < nx; i++ )
{
for ( j = 0; j < ny; j++ )
{
x = ( i - nx / 2 + 0.5 ) * dx;
y = ( j - ny / 2 + 0.5 ) * dy;
xg[i][j] = x;
yg[i][j] = y;
u[i][j] = y;
v[i][j] = -x;
}
}
// Plot vectors with default arrows
pls.env( xmin, xmax, ymin, ymax, 0, 0 );
pls.lab( "(x)", "(y)", "#frPLplot Example 22 - circulation" );
pls.col0( 2 );
pls.vect( u, v, 0.0, xg, yg );
pls.col0( 1 );
}
// Vector plot of flow through a constricted pipe
void constriction( int astyle )
{
int i, j;
double dx, dy, x, y;
double xmin, xmax, ymin, ymax;
double Q, b, dbdx;
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;
for ( i = 0; i < nx; i++ )
{
for ( j = 0; j < ny; j++ )
{
x = ( i - nx / 2 + 0.5 ) * dx;
y = ( j - ny / 2 + 0.5 ) * dy;
xg[i][j] = x;
yg[i][j] = y;
b = ymax / 4.0 * ( 3 - Math.cos( Math.PI * x / xmax ) );
if ( Math.abs( y ) < b )
{
dbdx = ymax / 4.0 * Math.sin( Math.PI * x / xmax ) *
Math.PI / xmax * y / b;
u[i][j] = Q * ymax / b;
v[i][j] = dbdx * u[i][j];
}
else
{
u[i][j] = 0.0;
v[i][j] = 0.0;
}
}
}
pls.env( xmin, xmax, ymin, ymax, 0, 0 );
pls.lab( "(x)", "(y)", "#frPLplot Example 22 - constriction (arrow style " + astyle + ")" );
pls.col0( 2 );
pls.vect( u, v, -1.0, xg, yg );
pls.col0( 1 );
}
//
// Vector plot of flow through a constricted pipe
// with a coordinate transform
//
void constriction2( )
{
int i, j;
double dx, dy, x, y;
double xmin, xmax, ymin, ymax;
double Q, b, dbdx;
double[] clev = new double[nc];
Transform transform = new Transform();
dx = 1.0;
dy = 1.0;
xmin = -nx / 2 * dx;
xmax = nx / 2 * dx;
ymin = -ny / 2 * dy;
ymax = ny / 2 * dy;
pls.stransform( transform, xmax );
Q = 2.0;
for ( i = 0; i < nx; i++ )
{
x = ( i - nx / 2 + 0.5 ) * dx;
for ( j = 0; j < ny; j++ )
{
y = ( j - ny / 2 + 0.5 ) * dy;
xg[i][j] = x;
yg[i][j] = y;
b = ymax / 4.0 * ( 3 - Math.cos( Math.PI * x / xmax ) );
u[i][j] = Q * ymax / b;
v[i][j] = 0.0;
}
}
for ( i = 0; i < nc; i++ )
{
clev[i] = Q + i * Q / ( nc - 1 );
}
pls.env( xmin, xmax, ymin, ymax, 0, 0 );
pls.lab( "(x)", "(y)", "#frPLplot Example 22 - constriction with plstransform" );
pls.col0( 2 );
pls.shades( u, xmin + dx / 2, xmax - dx / 2,
ymin + dy / 2, ymax - dy / 2,
clev, 0, 1, 1.0, 0, xg, yg );
pls.vect( u, v, -1.0, xg, yg );
// Plot edges using plpath (which accounts for coordinate transformation) rather than plline
pls.path( nseg, xmin, ymax, xmax, ymax );
pls.path( nseg, xmin, ymin, xmax, ymin );
pls.col0( 1 );
pls.stransform( null, null );
}
// Vector plot of the gradient of a shielded potential (see example 9)
void potential()
{
final int nper = 100;
final int nlevel = 10;
int i, j, nr, ntheta;
double eps, q1, d1, q1i, d1i, q2, d2, q2i, d2i;
double div1, div1i, div2, div2i;
double[][] z;
double r, theta, x, y, dz, rmax;
double[] xmaxmin = new double[2];
double[] ymaxmin = new double[2];
double[] zmaxmin = new double[2];
double[] px = new double[nper];
double[] py = new double[nper];
double[] clevel = new double[nlevel];
nr = nx;
ntheta = ny;
// Create data to be plotted
z = new double[nr][ntheta];
// 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 = Math.pow( rmax, 2. ) / d1;
q2 = -1.;
d2 = rmax / 4.;
q2i = -q2 * rmax / d2;
d2i = Math.pow( rmax, 2. ) / d2;
for ( i = 0; i < nr; i++ )
{
r = 0.5 + i;
for ( j = 0; j < ntheta; j++ )
{
theta = 2. * Math.PI / ( ntheta - 1 ) * ( 0.5 + j );
x = r * Math.cos( theta );
y = r * Math.sin( theta );
xg[i][j] = x;
yg[i][j] = y;
div1 = Math.sqrt( Math.pow( x - d1, 2. ) + Math.pow( y - d1, 2. ) + Math.pow( eps, 2. ) );
div1i = Math.sqrt( Math.pow( x - d1i, 2. ) + Math.pow( y - d1i, 2. ) + Math.pow( eps, 2. ) );
div2 = Math.sqrt( Math.pow( x - d2, 2. ) + Math.pow( y + d2, 2. ) + Math.pow( eps, 2. ) );
div2i = Math.sqrt( Math.pow( x - d2i, 2. ) + Math.pow( y + d2i, 2. ) + Math.pow( eps, 2. ) );
z[i][j] = q1 / div1 + q1i / div1i + q2 / div2 + q2i / div2i;
u[i][j] = -q1 * ( x - d1 ) / Math.pow( div1, 3. ) - q1i * ( x - d1i ) / Math.pow( div1i, 3.0 )
- q2 * ( x - d2 ) / Math.pow( div2, 3. ) - q2i * ( x - d2i ) / Math.pow( div2i, 3. );
v[i][j] = -q1 * ( y - d1 ) / Math.pow( div1, 3. ) - q1i * ( y - d1i ) / Math.pow( div1i, 3.0 )
- q2 * ( y + d2 ) / Math.pow( div2, 3. ) - q2i * ( y + d2i ) / Math.pow( div2i, 3. );
}
}
f2mnmx( xg, nr, ntheta, xmaxmin );
f2mnmx( yg, nr, ntheta, ymaxmin );
f2mnmx( z, nr, ntheta, zmaxmin );
pls.env( xmaxmin[1], xmaxmin[0], ymaxmin[1], ymaxmin[0], 0, 0 );
pls.lab( "(x)", "(y)", "#frPLplot Example 22 - potential gradient vector plot" );
// Plot contours of the potential
dz = ( zmaxmin[0] - zmaxmin[1] ) / nlevel;
for ( i = 0; i < nlevel; i++ )
{
clevel[i] = zmaxmin[1] + ( i + 0.5 ) * dz;
}
pls.col0( 3 );
pls.lsty( 2 );
pls.cont( z, 1, nr, 1, ntheta, clevel, xg, yg );
pls.lsty( 1 );
pls.col0( 1 );
// Plot the vectors of the gradient of the potential
pls.col0( 2 );
pls.vect( u, v, 25.0, xg, yg );
pls.col0( 1 );
// Plot the perimeter of the cylinder
for ( i = 0; i < nper; i++ )
{
theta = ( 2. * Math.PI / ( nper - 1 ) ) * i;
px[i] = rmax * Math.cos( theta );
py[i] = rmax * Math.sin( theta );
}
pls.line( px, py );
}
void f2mnmx( double [][] f, int nx, int ny, double[] fmaxmin )
{
int i, j;
fmaxmin[0] = f[0][0];
fmaxmin[1] = fmaxmin[0];
for ( i = 0; i < nx; i++ )
{
for ( j = 0; j < ny; j++ )
{
fmaxmin[0] = MAX( fmaxmin[0], f[i][j] );
fmaxmin[1] = MIN( fmaxmin[1], f[i][j] );
}
}
}
public x22( String[] args )
{
boolean fill;
// Set of points making a polygon to use as the arrow
final double arrow_x[] = { -0.5, 0.5, 0.3, 0.5, 0.3, 0.5 };
final double arrow_y[] = { 0.0, 0.0, 0.2, 0.0, -0.2, 0.0 };
final double arrow2_x[] = { -0.5, 0.3, 0.3, 0.5, 0.3, 0.3 };
final double arrow2_y[] = { 0.0, 0.0, 0.2, 0.0, -0.2, 0.0 };
// Parse and process command line arguments
pls.parseopts( args, PL_PARSE_FULL | PL_PARSE_NOPROGRAM );
// Initialize plplot
pls.init();
nx = 20;
ny = 20;
nc = 11;
nseg = 20;
// Allocate arrays
u = new double[nx][ny];
v = new double[nx][ny];
xg = new double[nx][ny];
yg = new double[nx][ny];
circulation();
fill = false;
// Set arrow style using arrow_x and arrow_y then
// plot uMath.sing these arrows.
pls.svect( arrow_x, arrow_y, fill );
constriction( 1 );
// Set arrow style using arrow2_x and arrow2_y then
// plot using these filled arrows.
fill = true;
pls.svect( arrow2_x, arrow2_y, fill );
constriction( 2 );
constriction2();
pls.svect( null, null, false );
potential();
pls.end();
}
public static void main( String[] args )
{
new x22( args );
}
}
//--------------------------------------------------------------------------
// End of x22.java
//--------------------------------------------------------------------------
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