/* nag_1d_spline_fit (e02bec) Example Program.
 *
 * Copyright 1991 Numerical Algorithms Group.
 *
 * Mark 2, 1991.
 *
 * Mark 6 revised, 2000.
 * Mark 8 revised, 2004.
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nage02.h>

int main(void)
{
  Integer    exit_status = 0, j, m, nest, r;
  NagError   fail;
  Nag_Comm   warmstartinf;
  Nag_Spline spline;
  Nag_Start  start;
  double     fp, s, *sp = 0, txr, *weights = 0, *x = 0, *y = 0;

  INIT_FAIL(fail);

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

  warmstartinf.nag_w = 0;
  warmstartinf.nag_iw = 0;

  printf("nag_1d_spline_fit (e02bec) Example Program Results\n");
  scanf("%*[^\n]"); /* Skip heading in data file */
  /* Input the number of data points, followed by the data
   * points x, the function values y and the weights w.
   */
  scanf("%ld", &m);
  nest = m + 4;
  if (m >= 4)
    {
      if (!(weights = NAG_ALLOC(m, double)) ||
          !(x = NAG_ALLOC(m, double)) ||
          !(y = NAG_ALLOC(m, double)) ||
          !(sp = NAG_ALLOC(2*m-1, double)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      printf("Invalid m.\n");
      exit_status = 1;
      return exit_status;
    }
  start = Nag_Cold;
  for (r = 0; r < m; r++)
    scanf("%lf%lf%lf", &x[r], &y[r], &weights[r]);
  /* Read in successive values of s until end of data file. */
  while (scanf("%lf", &s) != EOF)
    {
      /* Determine the spline approximation. */
      /* nag_1d_spline_fit (e02bec).
       * Least-squares cubic spline curve fit, automatic knot
       * placement, one variable
       */
      nag_1d_spline_fit(start, m, x, y, weights, s, nest, &fp,
                        &warmstartinf, &spline, &fail);
      if (fail.code != NE_NOERROR)
        {
          printf("Error from nag_1d_spline_fit (e02bec).\n%s\n",
                  fail.message);
          exit_status = 1;
          goto END;
        }

      /* Evaluate the spline at each x point and midway
       * between x points, saving the results in sp.
       */
      for (r = 0; r < m; r++)
        {
          /* nag_1d_spline_evaluate (e02bbc).
           * Evaluation of fitted cubic spline, function only
           */
          nag_1d_spline_evaluate(x[r], &sp[(r-1)*2+2], &spline, &fail);
          if (fail.code != NE_NOERROR)
            {
              printf("Error from nag_1d_spline_fit (e02bec).\n%s\n",
                      fail.message);
              exit_status = 1;
              goto END;
            }
        }

      for (r = 0; r < m-1; r++)
        {
          txr = (x[r] + x[r+1]) / 2;
          /* nag_1d_spline_evaluate (e02bbc), see above. */
          nag_1d_spline_evaluate(txr, &sp[r*2+1], &spline, &fail);
          if (fail.code != NE_NOERROR)
            {
              printf(
                      "Error from nag_1d_spline_evaluate (e02bbc).\n%s\n",
                      fail.message);
              exit_status = 1;
              goto END;
            }
        }
      /* Output the results. */
      printf("\nCalling with smoothing factor s = %12.3e\n", s);
      printf("\nNumber of distinct knots = %ld\n\n", spline.n-6);
      printf("Distinct knots located at \n\n");
      for (j = 3; j < spline.n-3; j++)
        printf("%8.4f%s", spline.lamda[j],
                (j-3)%6 == 5 || j == spline.n-4?"\n":" ");
      printf("\n\n    J      B-spline coeff c\n\n");
      for (j = 0;  j < spline.n-4; ++j)
        printf("  %3ld  %13.4f\n", j+1, spline.c[j]);
      printf("\nWeighted sum of squared residuals fp = %12.3e\n", fp);
      if (fp == 0.0)
        printf("The spline is an interpolating spline\n");
      else if (spline.n == 8)
        printf("The spline is the weighted least-squares cubic"
                "polynomial\n");
      start = Nag_Warm;
    }
  /* Free memory allocated in spline and warmstartinf */
 END:
  NAG_FREE(spline.lamda);
  NAG_FREE(spline.c);
  NAG_FREE(warmstartinf.nag_w);
  NAG_FREE(warmstartinf.nag_iw);
  if (weights) NAG_FREE(weights);
  if (x) NAG_FREE(x);
  if (y) NAG_FREE(y);
  if (sp) NAG_FREE(sp);
  return exit_status;
}