Example 5 - extrapolation (C single precision)

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <ncarg/ncargC.h>
#include <ncarg/gks.h>
#include <ncarg/ngmath.h>

#define NUM 5000
#define NX    21
#define NY    21
#define IWTYPE 1
#define WKID   1

main()
{
  int  i, j, k, ier;
  float xi[NUM], yi[NUM], zi[NUM];
  float xo[NX], yo[NY], *output, outr[NY][NX];
  float xminin =  0.00, yminin =  0.00, xmaxin = 1.00, ymaxin = 1.00;
  float xminot = -0.21, yminot = -0.21, xmaxot = 1.21, ymaxot = 1.21;
  float rho = 3., theta = -70., phi = 40.;
 
/*
 *  Create random data in three space and define a function.
 */
  for (i = 0; i < NUM; i++) {
    xi[i] = xminin+(xmaxin-xminin)*((float) rand() / (float) RAND_MAX);
    yi[i] = yminin+(ymaxin-yminin)*((float) rand() / (float) RAND_MAX);
    zi[i] = (xi[i]-0.25)*(xi[i]-0.25) + (yi[i]-0.50)*(yi[i]-0.50);
  }
 
/*
 *  Create the output grid.
 */
  for (i = 0; i < NX; i++) {
    xo[i] = xminot + ( (float) i / (float) (NX-1)) * (xmaxot-xminot);
  }
  for (j = 0; j < NY; j++) {
    yo[j] = yminot + ( (float) j / (float) (NY-1)) * (ymaxot-yminot);
  }

/*
 *  Interpolate.
 */
  output = c_dsgrid2s(NUM, xi, yi, zi, NX, NY, xo, yo, &ier);
  if (ier != 0) {
    printf(" Error %d returned from c_dsgrid2s\n",ier);
    exit(1);
  }
  gopen_gks ("stdout",0);
  gopen_ws (WKID, NULL, IWTYPE);
  gactivate_ws(WKID);

/*
 *  Reverse the array indices for plotting with tdez2d, since
 *  c_dsgrid returns its array in column dominate order.
 */
  for (i = 0; i < NX; i++) {
    for (j = 0; j < NY; j++) {
      outr[j][i] = output[i*NY+j];
    }
  }
  c_tdez2d(NX, NY, xo, yo, &outr[0][0], rho, theta, phi, 6);
  c_frame();

  gdeactivate_ws(WKID);
  gclose_ws(WKID);
  gclose_gks();
}