NAG Library Manual, Mark 27.2
/* nag_tsa_uni_means (g13auc) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.2, 2021.
*/

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

int main(void) {
/* Scalars */
Integer exit_status, i, ngrps, m, n;

/* Arrays */
double *mean = 0, *range = 0, *z = 0;
NagError fail;

INIT_FAIL(fail);

exit_status = 0;

printf("nag_tsa_uni_means (g13auc) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%" NAG_IFMT "%*[^\n] ", &n, &m);
if (n >= m && m >= 1) {
ngrps = n / m;

/* Allocate arrays */
if (!(mean = NAG_ALLOC(ngrps, double)) ||
!(range = NAG_ALLOC(ngrps, double)) || !(z = NAG_ALLOC(n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

for (i = 1; i <= n; ++i)
scanf("%lf", &z[i - 1]);
scanf("%*[^\n] ");

printf("\n");

/* nag_tsa_uni_means (g13auc).
* Computes quantities needed for range-mean or standard
* deviation-mean plot
*/
nag_tsa_uni_means(n, z, m, Nag_UseRange, range, mean, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_tsa_uni_means (g13auc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

printf("   Range      Mean\n");
for (i = 1; i <= ngrps; i++)
printf("%8.3f  %8.3f\n", range[i - 1], mean[i - 1]);
}

END:
NAG_FREE(mean);
NAG_FREE(range);
NAG_FREE(z);

return exit_status;
}