NAG Library Manual, Mark 29
```/* nag_sum_withdraw_fft_real_1d_multi_rfmt (c06fpc) Example Program.
*
* Copyright 2023 Numerical Algorithms Group.
*
* Mark 29.0, 2023.
*/

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

int main(void) {
Integer exit_status = 0, i, j, m, n;
NagError fail;
double *trig = 0, *u = 0, *v = 0, *x = 0;

INIT_FAIL(fail);

printf(
"nag_sum_withdraw_fft_real_1d_multi_rfmt (c06fpc) Example Program Results\n");
/* Skip heading in data file */
scanf("%*[^\n]");
while (scanf("%" NAG_IFMT "%" NAG_IFMT "", &m, &n) != EOF)
{
if (m >= 1 && n >= 1) {
if (!(trig = NAG_ALLOC(2 * n, double)) ||
!(u = NAG_ALLOC(m * n, double)) || !(v = NAG_ALLOC(m * n, double)) ||
!(x = NAG_ALLOC(m * n, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
} else {
printf("Invalid m or n.\n");
exit_status = 1;
return exit_status;
}

printf("\n\nm = %2" NAG_IFMT "  n = %2" NAG_IFMT "\n", m, n);
/* Read in data and print out. */
for (j = 0; j < m; ++j)
for (i = 0; i < n; ++i)
scanf("%lf", &x[j * n + i]);
printf("\nOriginal data values\n\n");
for (j = 0; j < m; ++j) {
printf("    ");
for (i = 0; i < n; ++i)
printf("%10.4f%s", x[j * n + i],
(i % 6 == 5 && i != n - 1 ? "\n     " : ""));
printf("\n");
}
/* nag_sum_init_trig (c06gzc).
* Initialization function for other c06 functions
*/
nag_sum_init_trig(n, trig, &fail); /* Initialize trig array */
if (fail.code != NE_NOERROR) {
printf("Error from nag_sum_init_trig (c06gzc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
/* Calculate transforms */
/* nag_sum_withdraw_fft_real_1d_multi_rfmt (c06fpc).
* Multiple one-dimensional real discrete Fourier transforms
*/
nag_sum_withdraw_fft_real_1d_multi_rfmt(m, n, x, trig, &fail);
if (fail.code != NE_NOERROR) {
printf(
"Error from nag_sum_withdraw_fft_real_1d_multi_rfmt (c06fpc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
printf("\nDiscrete Fourier transforms in Hermitian format\n\n");
for (j = 0; j < m; ++j) {
printf("    ");
for (i = 0; i < n; ++i)
printf("%10.4f%s", x[j * n + i],
(i % 6 == 5 && i != n - 1 ? "\n     " : ""));
printf("\n");
}
/* Calculate full complex form of Hermitian result */
/* nag_sum_withdraw_convert_herm2complex_sep (c06gsc).
* Convert Hermitian sequences to general complex sequences
*/
nag_sum_withdraw_convert_herm2complex_sep(m, n, x, u, v, &fail);
printf("\nFourier transforms in full complex form\n\n");
for (j = 0; j < m; ++j) {
printf("Real");
for (i = 0; i < n; ++i)
printf("%10.4f%s", u[j * n + i],
(i % 6 == 5 && i != n - 1 ? "\n     " : ""));
printf("\nImag");
for (i = 0; i < n; ++i)
printf("%10.4f%s", v[j * n + i],
(i % 6 == 5 && i != n - 1 ? "\n     " : ""));
printf("\n\n");
}
/* Calculate inverse transforms */
/* Conjugate Hermitian sequences of transforms */
/* nag_sum_withdraw_conjugate_hermitian_mult_rfmt (c06gqc).
* Complex conjugate of multiple Hermitian sequences
*/
nag_sum_withdraw_conjugate_hermitian_mult_rfmt(m, n, x, &fail);
/* Transform to give inverse transforms */
/* nag_sum_withdraw_fft_hermitian_1d_multi_rfmt (c06fqc).
* Multiple one-dimensional Hermitian discrete Fourier
* transforms
*/
nag_sum_withdraw_fft_hermitian_1d_multi_rfmt(m, n, x, trig, &fail);
printf("\nOriginal data as restored by inverse transform\n\n");
for (j = 0; j < m; ++j) {
printf("    ");
for (i = 0; i < n; ++i)
printf("%10.4f%s", x[j * n + i],
(i % 6 == 5 && i != n - 1 ? "\n     " : ""));
printf("\n");
}
END:
NAG_FREE(trig);
NAG_FREE(u);
NAG_FREE(v);
NAG_FREE(x);
}
return exit_status;
}
```