NAG Library Manual, Mark 27.3
```/* nag_interp_dim1_monconv_eval (e01cfc) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.3, 2021.
*/

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

int main(void) {

/* Logicals */
Nag_Boolean negfor;
Nag_Boolean yfor;

/* Scalars */
Integer i, n, m;
Integer exit_status = 0;
double lambda = 0;

/* Arrays */
double *comm = 0, *fwd = 0, *val = 0, *x = 0, *xi = 0, *y = 0;
char cnegfor[40], cyfor[40];

/* Nag Types */
NagError fail;

INIT_FAIL(fail);

printf("nag_interp_dim1_monconv_eval (e01cfc) Example Program Results\n");
printf("\n");

/* Read dimensions of arrays from data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n]", &n, &m);

/* Allocate arrays accordingly */
if (!(x = NAG_ALLOC((n), double)) || !(y = NAG_ALLOC((n), double)) ||
!(comm = NAG_ALLOC((4 * n + 10), double)) ||
!(xi = NAG_ALLOC((m), double)) || !(val = NAG_ALLOC((m), double)) ||
!(fwd = NAG_ALLOC((m), double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Input whether negative forward differences are allowed, and whether */
/* supplied values are forward differences */
scanf("%39s", cnegfor);
scanf("%39s", cyfor);
scanf("%*[^\n] ");

negfor = (Nag_Boolean)nag_enum_name_to_value(cnegfor);
yfor = (Nag_Boolean)nag_enum_name_to_value(cyfor);

/* Read amelioration parameter value */
scanf("%lf%*[^\n]", &lambda);

/* Read x and y array values from data file */
for (i = 0; i < n; i++) {
scanf("%lf%lf%*[^\n]", &x[i], &y[i]);
}

/* Interpolation setup */
nag_interp_dim1_monconv_disc(n, lambda, negfor, yfor, x, y, comm, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_interp_dim1_monconv_disc (e01cec).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* Interpolate at values in range [0:x(n)+0.2] in steps of 0.1 */
printf("i     x       Rate    Forward\n");
for (i = 0; i < m; i++) {
xi[i] = ((double)i * 0.1);
}
nag_interp_dim1_monconv_eval(m, xi, val, fwd, comm, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_interp_dim1_monconv_eval (e01cfc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
for (i = 0; i < m; i++) {
printf("%3.3" NAG_IFMT " %7.2f %7.3f %7.3f\n", i, xi[i], val[i], fwd[i]);
}

END:
NAG_FREE(x);
NAG_FREE(y);
NAG_FREE(comm);
NAG_FREE(xi);
NAG_FREE(val);
NAG_FREE(fwd);

return exit_status;
}
```