/* make_gnuplotdata.c   sin(x)+cos(y) test data to file */
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(int argc, char *argv[]) /* give output file name */
{
  int nx=40;
  int ny=40;
  double xmin=0.0;
  double xmax=12.56;
  double ymin=0.0;
  double ymax=12.56;
  double x,y,z,dx,dy;
  int i,j;
  FILE * outp;

  if(argc>1)
  {
    outp=fopen(argv[1], "w");
    if(outp==NULL)
    {
      printf("can not open %s for writing \n", argv[1]);
      return 1;
    }
  }
  else
  {
    printf("provide file name to write. \n");
    return 0;
  }

  dx = (xmax-xmin)/(double)(nx-1);
  dy = (ymax-ymin)/(double)(ny-1);

  for(i=0; i<nx; i++)
  {
    x = xmin + dx*i;
    for(j=0; j<ny; j++)
    {
      y = ymin + dy*j;
      z = sin(x)+cos(y);
      fprintf(outp,"%f  %f  %f \n", x, y, z);
    }
    fprintf(outp," \n");
  }
  fclose(outp);
  return 0;
} /* end make_gnuplotdata.c */