libplplot-dev 5.10.0+dfsg-1 / usr / share / doc / libplplot12 / examples / c / x22c.c

// $Id: x22c.c 12827 2013-12-09 13:20:01Z andrewross $
//
//  Simple vector plot example
//  Copyright (C) 2004 Andrew Ross
//  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
//
//

#include "plcdemos.h"

void circulation( void );
void constriction( int astyle );
void transform( PLFLT x, PLFLT y, PLFLT *xt, PLFLT *yt, PLPointer data );
void constriction2( void );
void potential( void );
void f2mnmx( PLFLT **f, PLINT nx, PLINT ny, PLFLT *fnmin, PLFLT *fnmax );

// Pairs of points making the line segments used to plot the user defined arroW
static PLFLT arrow_x[6] = { -0.5, 0.5, 0.3, 0.5, 0.3, 0.5 };
static PLFLT arrow_y[6] = { 0.0, 0.0, 0.2, 0.0, -0.2, 0.0 };
static PLFLT arrow2_x[6] = { -0.5, 0.3, 0.3, 0.5, 0.3, 0.3 };
static PLFLT arrow2_y[6] = { 0.0, 0.0, 0.2, 0.0, -0.2, 0.0 };

//--------------------------------------------------------------------------
// main
//
// Generates several simple vector plots.
//--------------------------------------------------------------------------

//
// Vector plot of the circulation about the origin
//
void
circulation( void )
{
    int       i, j;
    PLFLT     dx, dy, x, y;
    PLcGrid2  cgrid2;
    PLFLT     **u, **v;
    const int nx = 20;
    const int ny = 20;
    PLFLT     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;

    plAlloc2dGrid( &cgrid2.xg, nx, ny );
    plAlloc2dGrid( &cgrid2.yg, nx, ny );
    plAlloc2dGrid( &u, nx, ny );
    plAlloc2dGrid( &v, nx, ny );

    cgrid2.nx = nx;
    cgrid2.ny = ny;

    // Create data - circulation around the origin.
    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;
            cgrid2.xg[i][j] = x;
            cgrid2.yg[i][j] = y;
            u[i][j]         = y;
            v[i][j]         = -x;
        }
    }

    // Plot vectors with default arrows
    plenv( xmin, xmax, ymin, ymax, 0, 0 );
    pllab( "(x)", "(y)", "#frPLplot Example 22 - circulation" );
    plcol0( 2 );
    plvect( (const PLFLT * const *) u, (const PLFLT * const *) v, nx, ny, 0.0, pltr2, (void *) &cgrid2 );
    plcol0( 1 );

    plFree2dGrid( cgrid2.xg, nx, ny );
    plFree2dGrid( cgrid2.yg, nx, ny );
    plFree2dGrid( u, nx, ny );
    plFree2dGrid( v, nx, ny );
}

//
// Vector plot of flow through a constricted pipe
//
void
constriction( int astyle )
{
    int       i, j;
    PLFLT     dx, dy, x, y;
    PLFLT     xmin, xmax, ymin, ymax;
    PLFLT     Q, b, dbdx;
    PLcGrid2  cgrid2;
    PLFLT     **u, **v;
    const int nx = 20;
    const int ny = 20;
    char      title[80];

    dx = 1.0;
    dy = 1.0;

    xmin = -nx / 2 * dx;
    xmax = nx / 2 * dx;
    ymin = -ny / 2 * dy;
    ymax = ny / 2 * dy;

    plAlloc2dGrid( &cgrid2.xg, nx, ny );
    plAlloc2dGrid( &cgrid2.yg, nx, ny );
    plAlloc2dGrid( &u, nx, ny );
    plAlloc2dGrid( &v, nx, ny );

    cgrid2.nx = nx;
    cgrid2.ny = ny;

    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;
            cgrid2.xg[i][j] = x;
            cgrid2.yg[i][j] = y;
            b = ymax / 4.0 * ( 3 - cos( M_PI * x / xmax ) );
            if ( fabs( y ) < b )
            {
                dbdx = ymax / 4.0 * sin( M_PI * x / xmax ) *
                       M_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;
            }
        }
    }

    plenv( xmin, xmax, ymin, ymax, 0, 0 );
    sprintf( title, "#frPLplot Example 22 - constriction (arrow style %d)", astyle );
    pllab( "(x)", "(y)", title );
    plcol0( 2 );
    plvect( (const PLFLT * const *) u, (const PLFLT * const *) v, nx, ny, -1.0, pltr2, (void *) &cgrid2 );
    plcol0( 1 );

    plFree2dGrid( cgrid2.xg, nx, ny );
    plFree2dGrid( cgrid2.yg, nx, ny );
    plFree2dGrid( u, nx, ny );
    plFree2dGrid( v, nx, ny );
}


//
// Global transform function for a constriction using data passed in
// This is the same transformation used in constriction.
//
void
transform( PLFLT x, PLFLT y, PLFLT *xt, PLFLT *yt, PLPointer data )
{
    PLFLT *trdata;
    PLFLT xmax;

    trdata = (PLFLT *) data;
    xmax   = *trdata;

    *xt = x;
    *yt = y / 4.0 * ( 3 - cos( M_PI * x / xmax ) );
}

//
// Vector plot of flow through a constricted pipe
// with a coordinate transform
//
void
constriction2( void )
{
    int       i, j;
    PLFLT     dx, dy, x, y;
    PLFLT     xmin, xmax, ymin, ymax;
    PLFLT     Q, b;
    PLcGrid2  cgrid2;
    PLFLT     **u, **v;
    const int nx = 20;
    const int ny = 20;
#define NC    11
    const int nc   = NC;
    const int nseg = 20;
    PLFLT     clev[NC];

    dx = 1.0;
    dy = 1.0;

    xmin = -nx / 2 * dx;
    xmax = nx / 2 * dx;
    ymin = -ny / 2 * dy;
    ymax = ny / 2 * dy;

    plstransform( transform, ( PLPointer ) & xmax );

    plAlloc2dGrid( &cgrid2.xg, nx, ny );
    plAlloc2dGrid( &cgrid2.yg, nx, ny );
    plAlloc2dGrid( &u, nx, ny );
    plAlloc2dGrid( &v, nx, ny );

    cgrid2.nx = nx;
    cgrid2.ny = ny;

    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;
            cgrid2.xg[i][j] = x;
            cgrid2.yg[i][j] = y;
            b       = ymax / 4.0 * ( 3 - cos( M_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 );
    }

    plenv( xmin, xmax, ymin, ymax, 0, 0 );
    pllab( "(x)", "(y)", "#frPLplot Example 22 - constriction with plstransform" );
    plcol0( 2 );
    plshades( (const PLFLT * const *) u, nx, ny, NULL,
        xmin + dx / 2, xmax - dx / 2, ymin + dy / 2, ymax - dy / 2,
        clev, nc, 0.0, 1, 1.0, plfill, 0, NULL, NULL );
    plvect( (const PLFLT * const *) u, (const PLFLT * const *) v, nx, ny,
        -1.0, pltr2, (void *) &cgrid2 );
    // Plot edges using plpath (which accounts for coordinate transformation) rather than plline
    plpath( nseg, xmin, ymax, xmax, ymax );
    plpath( nseg, xmin, ymin, xmax, ymin );
    plcol0( 1 );

    plFree2dGrid( cgrid2.xg, nx, ny );
    plFree2dGrid( cgrid2.yg, nx, ny );
    plFree2dGrid( u, nx, ny );
    plFree2dGrid( v, nx, ny );

    plstransform( NULL, NULL );
}


void
f2mnmx( PLFLT **f, PLINT nx, PLINT ny, PLFLT *fnmin, PLFLT *fnmax )
{
    int i, j;

    *fnmax = f[0][0];
    *fnmin = *fnmax;

    for ( i = 0; i < nx; i++ )
    {
        for ( j = 0; j < ny; j++ )
        {
            *fnmax = MAX( *fnmax, f[i][j] );
            *fnmin = MIN( *fnmin, f[i][j] );
        }
    }
}

//
// Vector plot of the gradient of a shielded potential (see example 9)
//
void
potential( void )
{
#if !defined ( WIN32 )
    const int nper   = 100;
    const int nlevel = 10;
    const int nr     = 20;
    const int ntheta = 20;
#else
#define nper      100
#define nlevel    10
#define nr        20
#define ntheta    20
#endif

    int      i, j;
    PLFLT    eps, q1, d1, q1i, d1i, q2, d2, q2i, d2i;
    PLFLT    div1, div1i, div2, div2i;
    PLFLT    **u, **v, **z, r, theta, x, y, dz;
    PLFLT    xmin, xmax, ymin, ymax, rmax, zmax, zmin;
    PLFLT    px[nper], py[nper], clevel[nlevel];
    PLcGrid2 cgrid2;


    // Create data to be plotted
    plAlloc2dGrid( &cgrid2.xg, nr, ntheta );
    plAlloc2dGrid( &cgrid2.yg, nr, ntheta );
    plAlloc2dGrid( &u, nr, ntheta );
    plAlloc2dGrid( &v, nr, ntheta );
    plAlloc2dGrid( &z, nr, ntheta );

    cgrid2.nx = nr;
    cgrid2.ny = 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 = (double) nr;

    eps = 2.;

    q1 = 1.;
    d1 = rmax / 4.;

    q1i = -q1 * rmax / d1;
    d1i = pow( rmax, 2. ) / d1;

    q2 = -1.;
    d2 = rmax / 4.;

    q2i = -q2 * rmax / d2;
    d2i = pow( rmax, 2. ) / d2;

    for ( i = 0; i < nr; i++ )
    {
        r = 0.5 + (double) i;
        for ( j = 0; j < ntheta; j++ )
        {
            theta           = 2. * M_PI / ( ntheta - 1 ) * ( 0.5 + (double) j );
            x               = r * cos( theta );
            y               = r * sin( theta );
            cgrid2.xg[i][j] = x;
            cgrid2.yg[i][j] = y;
            div1            = sqrt( pow( x - d1, 2. ) + pow( y - d1, 2. ) + pow( eps, 2. ) );
            div1i           = sqrt( pow( x - d1i, 2. ) + pow( y - d1i, 2. ) + pow( eps, 2. ) );
            div2            = sqrt( pow( x - d2, 2. ) + pow( y + d2, 2. ) + pow( eps, 2. ) );
            div2i           = sqrt( pow( x - d2i, 2. ) + pow( y + d2i, 2. ) + pow( eps, 2. ) );
            z[i][j]         = q1 / div1 + q1i / div1i + q2 / div2 + q2i / div2i;
            u[i][j]         = -q1 * ( x - d1 ) / pow( div1, 3. ) - q1i * ( x - d1i ) / pow( div1i, 3.0 )
                              - q2 * ( x - d2 ) / pow( div2, 3. ) - q2i * ( x - d2i ) / pow( div2i, 3. );
            v[i][j] = -q1 * ( y - d1 ) / pow( div1, 3. ) - q1i * ( y - d1i ) / pow( div1i, 3.0 )
                      - q2 * ( y + d2 ) / pow( div2, 3. ) - q2i * ( y + d2i ) / pow( div2i, 3. );
        }
    }

    f2mnmx( cgrid2.xg, nr, ntheta, &xmin, &xmax );
    f2mnmx( cgrid2.yg, nr, ntheta, &ymin, &ymax );
    f2mnmx( z, nr, ntheta, &zmin, &zmax );

    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 ) / (double) nlevel;
    for ( i = 0; i < nlevel; i++ )
    {
        clevel[i] = zmin + ( (double) i + 0.5 ) * dz;
    }
    plcol0( 3 );
    pllsty( 2 );
    plcont( (const PLFLT * const *) z, nr, ntheta, 1, nr, 1, ntheta, clevel, nlevel, pltr2, (void *) &cgrid2 );
    pllsty( 1 );
    plcol0( 1 );

    // Plot the vectors of the gradient of the potential
    plcol0( 2 );
    plvect( (const PLFLT * const *) u, (const PLFLT * const *) v, nr, ntheta, 25.0, pltr2, (void *) &cgrid2 );
    plcol0( 1 );

    // Plot the perimeter of the cylinder
    for ( i = 0; i < nper; i++ )
    {
        theta = ( 2. * M_PI / ( nper - 1 ) ) * (double) i;
        px[i] = rmax * cos( theta );
        py[i] = rmax * sin( theta );
    }
    plline( nper, px, py );

    plFree2dGrid( z, nr, ntheta );
    plFree2dGrid( cgrid2.xg, nr, ntheta );
    plFree2dGrid( cgrid2.yg, nr, ntheta );
    plFree2dGrid( u, nr, ntheta );
    plFree2dGrid( v, nr, ntheta );
}

int
main( int argc, const char *argv[] )
{
    PLINT narr, fill;

    // Parse and process command line arguments

    plparseopts( &argc, argv, PL_PARSE_FULL );

    // Initialize plplot

    plinit();

    circulation();

    narr = 6;
    fill = 0;

    // Set arrow style using arrow_x and arrow_y then
    // plot using these arrows.
    plsvect( arrow_x, arrow_y, narr, fill );
    constriction( 1 );

    // Set arrow style using arrow2_x and arrow2_y then
    // plot using these filled arrows.
    fill = 1;
    plsvect( arrow2_x, arrow2_y, narr, fill );
    constriction( 2 );

    constriction2();

    // Reset arrow style to the default by passing two
    // NULL arrays
    plsvect( NULL, NULL, 0, 0 );

    potential();

    plend();
    exit( 0 );
}