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Date: Mon, 10 Jan 1994 11:38:00 BDB
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From: BJ06@C53000.PETROBRAS.ANRJ.BR
Subject: VANDRPOL.CPP
Lines: 84
 
//
//+------------------------------------------------------------+
//+ Program VANDRPOL.CPP                                       +
//+ Plots isoclines of the Van Der Pol's ODE (VDP Oscillator): +
//+                y" - Mu*y'*(1 - y^2) + y = 0                +
//+ or                                                         +
//+                v(dv/dy) - Mu*v*(1 - y^2) + y = 0           +
//+ Isoclines are defined by (dv/dy) = k                       +
//+------------------------------------------------------------+
//+ KREYSZIG, E. - _Advanced Engineering Mathematics_ ,        +
//+                John Wiley & Sons, 1988, pp. 165-166        +
//+ Requires SVGA and SVGA256.BGI + SVGA256.H                  +
//+------------------------------------------------------------+
//+ Usage:                                                     +
//+      VANDRPOL <Mu> <ymin> <ymax> <vmin> <vmax>             +
//+ Example:                                                   +
//+      VANDRPOL 0.32 -5.0 5.0 -5.0 5.0                       +
//+ Try:                                                       +
//+      Mu     xmin     xmax     ymin     ymax                +
//+     0.1     -5.0      5.0     -5.0      5.0                +
//+   -3.95     -4.0      4.0     -4.0      4.0                +
//+    0.05     -5.0      5.0     -5.0      5.0                +
//+   -0.75     -5.0      5.0     -5.0      5.0                +
//+    8.75     -5.0      5.0     -5.0      5.0                +
//+------------------------------------------------------------+
//+ COMMENTS modified by N. Giffin at Fausto's request. May/94 +
//+------------------------------------------------------------+
//+ By Fausto A. A. Barbuto, January 8, 1994                   +
//+ [PS: This is probably NOT a fractal, but it's              +
//+      good-looking! :-)  ]                                  +
//+------------------------------------------------------------+
//
#include <stdio.h>
#include <conio.h>
#include <graphics.h>
#include <math.h>
#include <stdlib.h>
#include "Svga256.h"
 
//void far initgraph(int far *,int far *,char far *);
 
int huge DetectVGA256()
{
  int Vid=4;
  return Vid;
}
 
void main(int argc, char *argv[])
{
      double Mu, ymin, ymax, vmin, vmax;
      double y, v, k, const_scr=1.0, deltav, deltay;
      register int npix=1024, npiy=768;
      register int ny, nv, ipen;
      char *endptr;
      int graphdriver=DETECT;
      int graphmode;
 
      Mu = strtod(argv[1],&endptr);
      ymin = strtod(argv[2],&endptr);
      ymax = strtod(argv[3],&endptr);
      vmin = strtod(argv[4],&endptr);
      vmax = strtod(argv[5],&endptr);
 
      installuserdriver("Svga256",DetectVGA256);
      initgraph(&graphdriver, &graphmode, "c:\\borlandc\\bgi");
 
      deltay = (ymax-ymin)/(double)npix;
      deltav = (vmax-vmin)/(double)npiy;
 
      cleardevice();
      for (ny=0; ny<=npix-1; ny++) {
        y = ymin + (double)ny*deltay;
        for (k=-5.0; k<=5.0; k=k+0.025) {
          v = y/(Mu*(1.0-y*y) - k);
          nv = (int)((v - vmin)/deltav);
          ipen = 33 + (int)(1.5*(k+5.0));
          putpixel(ny,nv,ipen);
        }
     }
 
// Clean-up.
// Fecha a parte grafica.
 
      getch();
      closegraph();
      restorecrtmode();
}