# Example 2 - varying the exponent of the distances (C single precision)

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

#define NUM    6
#define NX    61
#define NY    61
#define IWTYPE 1
#define WKID   1

main()
{
int  i, j, k, ier;
float xi[] = {0.00, 1.00, 0.00, 1.00, 0.40, 0.75};
float yi[] = {0.00, 0.00, 1.00, 1.00, 0.20, 0.65};
float zi[] = {0.00, 0.00, 0.00, 0.00, 1.25, 0.80};
float xo[NX], yo[NY], xinc, yinc, *output, outr[NY][NX];
float rho =  3., theta = -45., phi =  55.;

/*
*  Create the output grid.
*/
xinc = 1./ (float) (NX-1);
yinc = 1./ (float) (NY-1);
for (i = 0; i < NX; i++) {
xo[i] = xinc * (float) i;
}
for (j = 0; j < NY; j++) {
yo[j] = yinc * (float) j;
}

/*
*  Exponent equals 0.5
*/
c_dssetr("exp", 0.5);
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();

/*
*  Exponent equals 1.0
*/
c_dssetr("exp", 1.0);
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);
}
/*
*  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();

/*
*  Exponent equals 5.0
*/
c_dssetr("exp", 5.0);
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);
}
/*
*  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();
}
```

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