/* nag_tsa_uni_autocorr (g13abc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.1, 2024.
 *
 */

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

int main(void) {

  Integer exit_status = 0, i, nk, nx;
  NagError fail;
  double mean, *r = 0, stat, *x = 0, xv;

  INIT_FAIL(fail);

  printf("nag_tsa_uni_autocorr (g13abc) Example Program Results\n");
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT " %" NAG_IFMT "", &nx, &nk);

  if (nk > 0 && nx > 1 && nk < nx) {
    if (!(r = NAG_ALLOC(nk, double)) || !(x = NAG_ALLOC(nx, double))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
  } else {
    printf("Invalid nx or nk.\n");
    exit_status = 1;
    return exit_status;
  }
  for (i = 0; i < nx; ++i)
    scanf("%lf", &x[i]);
  printf("\nThe first %2" NAG_IFMT " coefficients are required\n", nk);

  /* nag_tsa_uni_autocorr (g13abc).
   * Sample autocorrelation function
   */
  nag_tsa_uni_autocorr(x, nx, nk, &mean, &xv, r, &stat, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_tsa_uni_autocorr (g13abc).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }

  printf("The input array has sample mean %12.4f\n", mean);
  printf("The input array has sample variance %12.4f\n", xv);
  printf("The sample autocorrelation coefficients are\n\n");
  printf("   Lag    Coeff\n");
  for (i = 0; i < 10; ++i)
    printf("%6" NAG_IFMT "%10.4f\n", i + 1, r[i]);
  printf("\nThe value of stat is %12.4f\n", stat);
END:
  NAG_FREE(r);
  NAG_FREE(x);
  return exit_status;
}