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x09c.c

/* $Id: x09c.c,v 1.27 2004/06/14 21:51:54 rlaboiss Exp $

      Contour plot demo.

   This file is part of PLplot.

   PLplot is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Library 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

*/

#include "plcdemos.h"

#define XPTS    35            /* Data points in x */
#define YPTS    46            /* Data points in y */

#define XSPA    2./(XPTS-1)
#define YSPA    2./(YPTS-1)

/* polar plot data */
#define PERIMETERPTS 100
#define RPTS 40
#define THETAPTS 40

/* potential plot data */
#define PPERIMETERPTS 100
#define PRPTS 40
#define PTHETAPTS 64
#define PNLEVEL 20

static PLFLT clevel[11] =
{-1., -.8, -.6, -.4, -.2, 0, .2, .4, .6, .8, 1.};

/* Transformation function */

PLFLT tr[6] =
{XSPA, 0.0, -1.0, 0.0, YSPA, -1.0};

static void
mypltr(PLFLT x, PLFLT y, PLFLT *tx, PLFLT *ty, void *pltr_data)
{
    *tx = tr[0] * x + tr[1] * y + tr[2];
    *ty = tr[3] * x + tr[4] * y + tr[5];
}

static void polar()
/*polar contour plot example.*/
{
   int i,j;
   PLcGrid2 cgrid2;
   PLFLT **z;
   PLFLT px[PERIMETERPTS], py[PERIMETERPTS];
   PLFLT t, r, theta;
   PLFLT lev[10];

   plenv(-1., 1., -1., 1., 0, -2);
   plcol0(1);
       
/*Perimeter*/
   for (i = 0; i < PERIMETERPTS; i++) {
      t = (2.*PI/(PERIMETERPTS-1))*(double)i;
      px[i] = cos(t);
      py[i] = sin(t);
   }
   plline(PERIMETERPTS, px, py);
             
/*create data to be contoured.*/
   plAlloc2dGrid(&cgrid2.xg, RPTS, THETAPTS);
   plAlloc2dGrid(&cgrid2.yg, RPTS, THETAPTS);
   plAlloc2dGrid(&z, RPTS, THETAPTS);
   cgrid2.nx = RPTS;
   cgrid2.ny = THETAPTS;
   
   for (i = 0; i < RPTS; i++) {
      r = i/(double)(RPTS-1);
      for (j = 0; j < THETAPTS; j++) {
       theta = (2.*PI/(double)(THETAPTS-1))*(double)j;
       cgrid2.xg[i][j] = r*cos(theta);
       cgrid2.yg[i][j] = r*sin(theta);
       z[i][j] = r;
      }
   }

   for (i = 0; i < 10; i++) {
      lev[i] = 0.05 + 0.10*(double) i;
   }

   plcol0(2);
   plcont(z, RPTS, THETAPTS, 1, RPTS, 1, THETAPTS, lev, 10,
                    pltr2, (void *) &cgrid2);
   plcol0(1);
   pllab("", "", "Polar Contour Plot");
   plFree2dGrid(z, RPTS, THETAPTS);
   plFree2dGrid(cgrid2.xg, RPTS, THETAPTS);
   plFree2dGrid(cgrid2.yg, RPTS, THETAPTS);
}

/*--------------------------------------------------------------------------*\
 * f2mnmx
 *
 * Returns min & max of input 2d array.
\*--------------------------------------------------------------------------*/

static void
f2mnmx(PLFLT **f, PLINT nx, PLINT ny, PLFLT *fmin, PLFLT *fmax)
{
    int i, j;

    *fmax = f[0][0];
    *fmin = *fmax;

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

static void potential()
/*shielded potential contour plot example.*/
{
   int i,j;
   PLcGrid2 cgrid2;
   PLFLT rmax, xmin, xmax, x0, ymin, ymax, y0, zmin, zmax;
   PLFLT peps, xpmin, xpmax, ypmin, ypmax;
   PLFLT eps, q1, d1, q1i, d1i, q2, d2, q2i, d2i;
   PLFLT div1, div1i, div2, div2i;
   PLFLT **z;
   PLINT nlevelneg, nlevelpos;
   PLFLT dz, clevel, clevelneg[PNLEVEL], clevelpos[PNLEVEL];
   PLINT ncollin, ncolbox, ncollab;
   PLFLT px[PPERIMETERPTS], py[PPERIMETERPTS];
   PLFLT t, r, theta;

/*create data to be contoured.*/
   plAlloc2dGrid(&cgrid2.xg, PRPTS, PTHETAPTS);
   plAlloc2dGrid(&cgrid2.yg, PRPTS, PTHETAPTS);
   plAlloc2dGrid(&z, PRPTS, PTHETAPTS);
   cgrid2.nx = PRPTS;
   cgrid2.ny = PTHETAPTS;

   for (i = 0; i < PRPTS; i++) {
      r = 0.5 + (double) i;
      for (j = 0; j < PTHETAPTS; j++) {
       theta = (2.*PI/(double)(PTHETAPTS-1))*(0.5 + (double) j);
       cgrid2.xg[i][j] = r*cos(theta);
       cgrid2.yg[i][j] = r*sin(theta);
      }
   }

   rmax = r;
   f2mnmx(cgrid2.xg, PRPTS, PTHETAPTS, &xmin, &xmax);
   f2mnmx(cgrid2.yg, PRPTS, PTHETAPTS, &ymin, &ymax);
   x0 = (xmin + xmax)/2.;
   y0 = (ymin + ymax)/2.;

   /* Expanded limits */
   peps = 0.05;
   xpmin = xmin - fabs(xmin)*peps;
   xpmax = xmax + fabs(xmax)*peps;
   ypmin = ymin - fabs(ymin)*peps;
   ypmax = ymax + fabs(ymax)*peps;

   /* 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.
   */

   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 < PRPTS; i++) {
      for (j = 0; j < PTHETAPTS; j++) {
       div1 = sqrt(pow(cgrid2.xg[i][j]-d1, 2.) + pow(cgrid2.yg[i][j]-d1, 2.) + pow(eps, 2.));
       div1i = sqrt(pow(cgrid2.xg[i][j]-d1i, 2.) + pow(cgrid2.yg[i][j]-d1i, 2.) + pow(eps, 2.));
       div2 = sqrt(pow(cgrid2.xg[i][j]-d2, 2.) + pow(cgrid2.yg[i][j]+d2, 2.) + pow(eps, 2.));
       div2i = sqrt(pow(cgrid2.xg[i][j]-d2i, 2.) + pow(cgrid2.yg[i][j]+d2i, 2.) + pow(eps, 2.));
       z[i][j] = q1/div1 + q1i/div1i + q2/div2 + q2i/div2i;
      }
   }
   f2mnmx(z, PRPTS, PTHETAPTS, &zmin, &zmax);
/*   printf("%.15g %.15g %.15g %.15g %.15g %.15g %.15g %.15g \n",
        q1, d1, q1i, d1i, q2, d2, q2i, d2i);
   printf("%.15g %.15g %.15g %.15g %.15g %.15g \n",
        xmin, xmax, ymin, ymax, zmin, zmax); */

   /* Positive and negative contour levels.*/
   dz = (zmax-zmin)/(double) PNLEVEL;
   nlevelneg = 0;
   nlevelpos = 0;
   for (i = 0; i < PNLEVEL; i++) {
      clevel = zmin + ((double) i + 0.5)*dz;
      if (clevel <= 0.)
      clevelneg[nlevelneg++] = clevel;
      else
      clevelpos[nlevelpos++] = clevel;
   }
   /* Colours! */
   ncollin = 11;
   ncolbox = 1;
   ncollab = 2;

   /* Finally start plotting this page! */
   pladv(0);
   plcol0(ncolbox);

   plvpas(0.1, 0.9, 0.1, 0.9, 1.0);
   plwind(xpmin, xpmax, ypmin, ypmax);
   plbox("", 0., 0, "", 0., 0);

   plcol0(ncollin);
   if(nlevelneg >0) {
      /* Negative contours */
      pllsty(2);
      plcont(z, PRPTS, PTHETAPTS, 1, PRPTS, 1, PTHETAPTS,
           clevelneg, nlevelneg, pltr2, (void *) &cgrid2);
   }

   if(nlevelpos >0) {
      /* Positive contours  */
      pllsty(1);
      plcont(z, PRPTS, PTHETAPTS, 1, PRPTS, 1, PTHETAPTS,
           clevelpos, nlevelpos, pltr2, (void *) &cgrid2);
   }
             
   /* Draw outer boundary  */
   for (i = 0; i < PPERIMETERPTS; i++) {
      t = (2.*PI/(PPERIMETERPTS-1))*(double)i;
      px[i] = x0 + rmax*cos(t);
      py[i] = y0 + rmax*sin(t);
   }

   plcol0(ncolbox);
   plline(PPERIMETERPTS, px, py);
             
   plcol0(ncollab);
   pllab("", "", "Shielded potential of charges in a conducting sphere");

   plFree2dGrid(z, PRPTS, PTHETAPTS);
   plFree2dGrid(cgrid2.xg, PRPTS, PTHETAPTS);
   plFree2dGrid(cgrid2.yg, PRPTS, PTHETAPTS);
}
  

/*--------------------------------------------------------------------------*\
 * main
 *
 * Does several contour plots using different coordinate mappings.
\*--------------------------------------------------------------------------*/

int
main(int argc, char *argv[])
{
    int i, j;
    PLFLT xx, yy, argx, argy, distort;
    static PLINT mark = 1500, space = 1500;

    PLFLT **z, **w;
    PLFLT xg1[XPTS], yg1[YPTS];
    PLcGrid  cgrid1;
    PLcGrid2 cgrid2;

/* Parse and process command line arguments */

    (void) plParseOpts(&argc, argv, PL_PARSE_FULL);

/* Initialize plplot */

    plinit();

/* Set up function arrays */

    plAlloc2dGrid(&z, XPTS, YPTS);
    plAlloc2dGrid(&w, XPTS, YPTS);

    for (i = 0; i < XPTS; i++) {
      xx = (double) (i - (XPTS / 2)) / (double) (XPTS / 2);
      for (j = 0; j < YPTS; j++) {
          yy = (double) (j - (YPTS / 2)) / (double) (YPTS / 2) - 1.0;
          z[i][j] = xx * xx - yy * yy;
          w[i][j] = 2 * xx * yy;
      }
    }

/* Set up grids */

    cgrid1.xg = xg1;
    cgrid1.yg = yg1;
    cgrid1.nx = XPTS;
    cgrid1.ny = YPTS;

    plAlloc2dGrid(&cgrid2.xg, XPTS, YPTS);
    plAlloc2dGrid(&cgrid2.yg, XPTS, YPTS);
    cgrid2.nx = XPTS;
    cgrid2.ny = YPTS;

    for (i = 0; i < XPTS; i++) {
      for (j = 0; j < YPTS; j++) {
          mypltr((PLFLT) i, (PLFLT) j, &xx, &yy, NULL);

          argx = xx * PI/2;
          argy = yy * PI/2;
          distort = 0.4;

          cgrid1.xg[i] = xx + distort * cos(argx);
          cgrid1.yg[j] = yy - distort * cos(argy);

          cgrid2.xg[i][j] = xx + distort * cos(argx) * cos(argy);
          cgrid2.yg[i][j] = yy - distort * cos(argx) * cos(argy);
      }
    }

/* Plot using identity transform */
/*
    plenv(-1.0, 1.0, -1.0, 1.0, 0, 0);
    plcol0(2);
    plcont(z, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11, mypltr, NULL);
    plstyl(1, &mark, &space);
    plcol0(3);
    plcont(w, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11, mypltr, NULL);
    plstyl(0, &mark, &space);
    plcol0(1);
    pllab("X Coordinate", "Y Coordinate", "Streamlines of flow");
*/
    pl_setcontlabelparam(0.006, 0.3, 0.1, 1);
    plenv(-1.0, 1.0, -1.0, 1.0, 0, 0);
    plcol0(2);
    plcont(z, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11, mypltr, NULL);
    plstyl(1, &mark, &space);
    plcol0(3);
    plcont(w, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11, mypltr, NULL);
    plstyl(0, &mark, &space);
    plcol0(1);
    pllab("X Coordinate", "Y Coordinate", "Streamlines of flow");
    pl_setcontlabelparam(0.006, 0.3, 0.1, 0);
    
/* Plot using 1d coordinate transform */

    plenv(-1.0, 1.0, -1.0, 1.0, 0, 0);
    plcol0(2);
    plcont(z, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr1, (void *) &cgrid1);

    plstyl(1, &mark, &space);
    plcol0(3);
    plcont(w, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr1, (void *) &cgrid1);
    plstyl(0, &mark, &space);
    plcol0(1);
    pllab("X Coordinate", "Y Coordinate", "Streamlines of flow");
    /*
    pl_setcontlabelparam(0.006, 0.3, 0.1, 1);
    plenv(-1.0, 1.0, -1.0, 1.0, 0, 0);
    plcol0(2);
    plcont(z, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr1, (void *) &cgrid1);

    plstyl(1, &mark, &space);
    plcol0(3);
    plcont(w, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr1, (void *) &cgrid1);
    plstyl(0, &mark, &space);
    plcol0(1);
    pllab("X Coordinate", "Y Coordinate", "Streamlines of flow");
    pl_setcontlabelparam(0.006, 0.3, 0.1, 0);
    */
/* Plot using 2d coordinate transform */

    plenv(-1.0, 1.0, -1.0, 1.0, 0, 0);
    plcol0(2);
    plcont(z, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr2, (void *) &cgrid2);

    plstyl(1, &mark, &space);
    plcol0(3);
    plcont(w, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr2, (void *) &cgrid2);
    plstyl(0, &mark, &space);
    plcol0(1);
    pllab("X Coordinate", "Y Coordinate", "Streamlines of flow");
    /*
    pl_setcontlabelparam(0.006, 0.3, 0.1, 1);
    plenv(-1.0, 1.0, -1.0, 1.0, 0, 0);
    plcol0(2);
    plcont(z, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr2, (void *) &cgrid2);

    plstyl(1, &mark, &space);
    plcol0(3);
    plcont(w, XPTS, YPTS, 1, XPTS, 1, YPTS, clevel, 11,
         pltr2, (void *) &cgrid2);
    plstyl(0, &mark, &space);
    plcol0(1);
    pllab("X Coordinate", "Y Coordinate", "Streamlines of flow");
    */
    pl_setcontlabelparam(0.006, 0.3, 0.1, 0);
    polar();
    /*
    pl_setcontlabelparam(0.006, 0.3, 0.1, 1);
    polar();
    */
    pl_setcontlabelparam(0.006, 0.3, 0.1, 0);
    potential();
    /*
    pl_setcontlabelparam(0.006, 0.3, 0.1, 1);
    potential();
    */

/* Clean up */
           
    plFree2dGrid(z, XPTS, YPTS);
    plFree2dGrid(w, XPTS, YPTS);
    plFree2dGrid(cgrid2.xg, XPTS, YPTS);
    plFree2dGrid(cgrid2.yg, XPTS, YPTS);
   
    plend();

    exit(0);
}

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