NAG Library Manual, Mark 28.7
```/* nag_tsa_multi_gain_bivar (g13cfc) Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
*
* Mark 28.7, 2022.
*
*/

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

#define L 80
#define KC 8 * L
#define NGMAX KC
#define NXYMAX 300

int main(void) {

Complex *xyg = 0;
Integer exit_status = 0, i, is, j, kc = KC, l = L, mw, ng, nxy;
NagError fail;
double *gn = 0, *gnlw = 0, *gnup = 0, *ph = 0, *phlw = 0, *phup = 0, pw, pxy,
*stats = 0;
double *x = 0, *xg = 0, *y = 0, *yg = 0;

INIT_FAIL(fail);

printf("nag_tsa_multi_gain_bivar (g13cfc) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT " ", &nxy);
if (nxy > 0 && nxy <= NXYMAX) {
if (!(stats = NAG_ALLOC(4, double)) || !(x = NAG_ALLOC(KC, double)) ||
!(y = NAG_ALLOC(KC, double)) || !(gnlw = NAG_ALLOC(NGMAX, double)) ||
!(gnup = NAG_ALLOC(NGMAX, double)) ||
!(phlw = NAG_ALLOC(NGMAX, double)) ||
!(phup = NAG_ALLOC(NGMAX, double)) ||
!(gn = NAG_ALLOC(NGMAX, double)) || !(ph = NAG_ALLOC(NGMAX, double))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
for (i = 1; i <= nxy; ++i)
scanf("%lf ", &x[i - 1]);
for (i = 1; i <= nxy; ++i)
scanf("%lf ", &y[i - 1]);

/* Set parameters for call to nag_tsa_uni_spectrum_daniell (g13cbc) and
* g13cdc with mean correction and 10 percent taper
*/
pxy = 0.1;
/* Window shape parameter and zero covariance at lag 16 */
pw = 0.5;
mw = 16;
/* Alignment shift of 3 */
is = 3;

/* Obtain univariate spectrum for the x and the y series */
/* nag_tsa_uni_spectrum_daniell (g13cbc).
* Univariate time series, smoothed sample spectrum using
* spectral smoothing by the trapezium frequency (Daniell)
* window
*/
nag_tsa_uni_spectrum_daniell(nxy, Nag_Mean, pxy, mw, pw, l, kc,
Nag_Unlogged, x, &xg, &ng, stats, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_tsa_uni_spectrum_daniell (g13cbc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* nag_tsa_uni_spectrum_daniell (g13cbc), see above. */
nag_tsa_uni_spectrum_daniell(nxy, Nag_Mean, pxy, mw, pw, l, kc,
Nag_Unlogged, y, &yg, &ng, stats, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_tsa_uni_spectrum_daniell (g13cbc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* Obtain cross spectrum of the bivariate series */
/* nag_tsa_multi_spectrum_daniell (g13cdc).
* Multivariate time series, smoothed sample cross spectrum
* using spectral smoothing by the trapezium frequency
* (Daniell) window
*/
nag_tsa_multi_spectrum_daniell(nxy, Nag_Mean, pxy, mw, is, pw, l, kc, x, y,
&xyg, &ng, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_tsa_multi_spectrum_daniell (g13cdc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

/* nag_tsa_multi_gain_bivar (g13cfc).
* Multivariate time series, gain, phase, bounds, univariate
* and bivariate (cross) spectra
*/
nag_tsa_multi_gain_bivar(xg, yg, xyg, ng, stats, gn, gnlw, gnup, ph, phlw,
phup, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_tsa_multi_gain_bivar (g13cfc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}

printf("\n");
printf("               The gain\n\n");
printf("                       Lower     Upper\n");
printf("           Value       bound     bound\n\n");
for (j = 1; j <= ng; ++j)
printf("%6" NAG_IFMT " %10.4f %10.4f %10.4f\n", j - 1, gn[j - 1],
gnlw[j - 1], gnup[j - 1]);
printf("\n              The phase\n\n");
printf("                       Lower     Upper\n");
printf("           Value       bound     bound\n\n");
for (j = 1; j <= ng; ++j)
printf("%6" NAG_IFMT " %10.4f %10.4f %10.4f\n", j - 1, ph[j - 1],
phlw[j - 1], phup[j - 1]);
}
NAG_FREE(xg);
NAG_FREE(yg);
NAG_FREE(xyg);
END:
NAG_FREE(stats);
NAG_FREE(x);
NAG_FREE(y);
NAG_FREE(gnlw);
NAG_FREE(gnup);
NAG_FREE(phlw);
NAG_FREE(phup);
NAG_FREE(gn);
NAG_FREE(ph);
return exit_status;
}
```