NAG Library Manual, Mark 30.2
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_fit_dim1_spline_deriv (e02bcc) Example Program.
 *
 * Copyright 2024 Numerical Algorithms Group.
 *
 * Mark 30.2, 2024.
 *
 */

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

int main(void) {
  Integer exit_status = 0, i, j, l, m, ncap, ncap7;
  NagError fail;
  Nag_DerivType derivs;
  Nag_Spline spline;
  double s[4], x;

  INIT_FAIL(fail);

  /* Initialize spline */
  spline.lamda = 0;
  spline.c = 0;

  printf("nag_fit_dim1_spline_deriv (e02bcc) Example Program Results\n");
  scanf("%*[^\n]"); /* Skip heading in data file */
  while (scanf("%" NAG_IFMT "%" NAG_IFMT "", &ncap, &m) != EOF)
  {
    if (m <= 0) {
      printf("Invalid m.\n");
      exit_status = 1;
      return exit_status;
    }
    if (ncap > 0) {
      ncap7 = ncap + 7;
      spline.n = ncap7;
      if (!(spline.c = NAG_ALLOC(ncap7, double)) ||
          !(spline.lamda = NAG_ALLOC(ncap7, double))) {
        printf("Allocation failure\n");
        exit_status = -1;
        goto END;
      }
    } else {
      printf("Invalid ncap.\n");
      exit_status = 1;
      return exit_status;
    }
    for (j = 0; j < ncap7; j++)
      scanf("%lf", &(spline.lamda[j]));
    for (j = 0; j < ncap + 3; j++)
      scanf("%lf", &(spline.c[j]));
    printf("        x             Spline    1st deriv  "
           "2nd deriv   3rd deriv");
    for (i = 1; i <= m; i++) {
      scanf("%lf", &x);
      derivs = Nag_LeftDerivs;
      for (j = 1; j <= 2; j++) {
        /* nag_fit_dim1_spline_deriv (e02bcc).
         * Evaluation of fitted cubic spline, function and
         * derivatives
         */
        nag_fit_dim1_spline_deriv(derivs, x, s, &spline, &fail);
        if (fail.code != NE_NOERROR) {
          printf("Error from nag_fit_dim1_spline_deriv (e02bcc).\n%s\n",
                 fail.message);
          exit_status = 1;
          goto END;
        }

        if (derivs == Nag_LeftDerivs) {
          printf("\n\n%11.4f   Left", x);
          for (l = 0; l < 4; l++)
            printf("%11.4f", s[l]);
        } else {
          printf("\n%11.4f  Right", x);
          for (l = 0; l < 4; l++)
            printf("%11.4f", s[l]);
        }
        derivs = Nag_RightDerivs;
      }
    }
    printf("\n");
  END:
    NAG_FREE(spline.c);
    NAG_FREE(spline.lamda);
  }
  return exit_status;
}