```/* nag_monotonic_deriv (e01bgc) Example Program.
*
* Copyright 2017 Numerical Algorithms Group.
*
* Mark 26.1, 2017.
*/

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nage01.h>

int main(void)
{
Integer exit_status = 0, i, m, n, r;
NagError fail;
double *d = 0, *f = 0, *pd = 0, *pf = 0, *px = 0, step, *x = 0;

INIT_FAIL(fail);

printf("nag_monotonic_deriv (e01bgc) Example Program Results\n");
scanf("%*[^\n]"); /* Skip heading in data file */
scanf("%" NAG_IFMT "", &n);
if (n >= 2) {
if (!(x = NAG_ALLOC(n, double)) ||
!(f = NAG_ALLOC(n, double)) || !(d = NAG_ALLOC(n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
}
else {
printf("Invalid n.\n");
exit_status = 1;
return exit_status;
}
for (r = 0; r < n; r++)
scanf("%lf%lf%lf", &x[r], &f[r], &d[r]);
scanf("%" NAG_IFMT "", &m);
if (m >= 1) {
if (!(pd = NAG_ALLOC(m, double)) ||
!(pf = NAG_ALLOC(m, double)) || !(px = NAG_ALLOC(m, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
}
else {
printf("Invalid m.\n");
exit_status = 1;
return exit_status;
}
/* compute m equally spaced points from x[0] to x[n-1]. */
step = (x[n - 1] - x[0]) / (double) (m - 1);
for (i = 0; i < m; i++)
px[i] = MIN(x[0] + i * step, x[n - 1]);
/* nag_monotonic_deriv (e01bgc).
* Evaluation of interpolant computed by
* nag_monotonic_interpolant (e01bec), function and first
* derivative
*/
nag_monotonic_deriv(n, x, f, d, m, px, pf, pd, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_monotonic_deriv (e01bgc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
printf("                            Interpolated");
printf("      Interpolated\n");
printf("       Abscissa                Value");
printf("           Derivative\n");
for (i = 0; i < m; i++)
printf("%15.4f      %15.4f      %15.3e\n", px[i], pf[i], pd[i]);
END:
NAG_FREE(x);
NAG_FREE(pd);
NAG_FREE(pf);
NAG_FREE(px);
NAG_FREE(f);
NAG_FREE(d);
return exit_status;
}
```