```/* nag_smooth_data_order (g10zac) Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
*
* Mark 27.0, 2019.
*/

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

int main(void)
{
Integer exit_status = 0, i, *iwrk = 0, n, nord;
NagError fail;
char weight[2];
double rss, *weights = 0, *wtord = 0, *wtptr, *x = 0, *xord = 0, *y = 0;
double *yord = 0;

INIT_FAIL(fail);

printf("nag_smooth_data_order (g10zac) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "", &n);
if (!(x = NAG_ALLOC(n, double))
|| !(y = NAG_ALLOC(n, double))
|| !(weights = NAG_ALLOC(n, double))
|| !(xord = NAG_ALLOC(n, double))
|| !(yord = NAG_ALLOC(n, double))
|| !(wtord = NAG_ALLOC(n, double))
|| !(iwrk = NAG_ALLOC(n, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}
scanf(" %1s ", weight);
for (i = 1; i <= n; ++i)
scanf("%lf %lf", &x[i - 1], &y[i - 1]);
if (*weight == 'W')
wtptr = weights;
else
wtptr = 0;

/* nag_smooth_data_order (g10zac).
* Reorder data to give ordered distinct observations
*/
nag_smooth_data_order(n, x, y, wtptr, &nord, xord, yord, wtord, &rss, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_smooth_data_order (g10zac).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Print results */
printf("\n");
printf("%s%6" NAG_IFMT "\n", "Number of distinct observations = ", nord);
printf("%s%13.5f\n", "Residual sum of squares = ", rss);
printf("\n");
printf("              X                 Y              WEIGHTS\n");
for (i = 1; i <= nord; ++i)
printf("     %13.5f     %13.5f     %13.5f\n", xord[i - 1],
yord[i - 1], wtord[i - 1]);
END:
NAG_FREE(x);
NAG_FREE(y);
NAG_FREE(weights);
NAG_FREE(xord);
NAG_FREE(yord);
NAG_FREE(wtord);
NAG_FREE(iwrk);
return exit_status;
}
```