/* nag_simple_linear_regression(g02cac) Example Program
 *
 * Copyright 1992 Numerical Algorithms Group.
 *
 * Mark 3, 1992.
 */

#include <nag.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <nagg02.h>

#define NMAX 10
int main(void)
{
  Nag_SumSquare mean;
  char m, w;
  Integer i, n;
  double x[NMAX], y[NMAX], wt[NMAX];
  double a, b, err_a, err_b, rsq, rss, df;
  double *wtptr;

  Vprintf("g02cac Example Program Results\n");
  /* Skip heading in data file */
  Vscanf("%*[^\n]");
  Vscanf(" %c %c",&m, &w);
  Vscanf("%ld", &n);
  if (n>=1 && n<=NMAX)
    {
      if (m == 'M' || m == 'm')
        mean = Nag_AboutMean;
      else
        mean = Nag_AboutZero;
      if (w == 'W' || w == 'w')
        {
          wtptr = wt;
          for(i = 0; i < n; ++i)
            Vscanf("%lf%lf%lf", &x[i], &y[i], &wt[i]);
        }
      else
        {
          wtptr = (double *)0;
          for(i = 0; i < n; ++i)
            Vscanf("%lf%lf", &x[i], &y[i]);
        }

      g02cac(mean, n, x, y, wtptr, &a, &b, &err_a, &err_b, &rsq, &rss,
             &df, NAGERR_DEFAULT);


      if (mean == Nag_AboutMean)
        {
          Vprintf("\nRegression constant a = %6.4f\n\n", a);
          Vprintf("Standard error of the regression constant a = %6.4f\n\n",
                  err_a);
        }

      Vprintf("Regression coefficient b = %6.4f\n\n", b);
      Vprintf("Standard error of the regression coefficient b = %6.4f\n\n",
              err_b);

      Vprintf("The regression coefficient of determination = %6.4f\n\n", rsq);
      Vprintf("The sum of squares of the residuals about the "
              "regression = %6.4f\n\n", rss);
      Vprintf("Number of degrees of freedom about the "
              "regression = %6.4f\n\n",df);
    }
  else
    {
      Vfprintf(stderr, "n is out of range:"
               " n = %-3ld\n",n);
      return EXIT_FAILURE;
    }
  return EXIT_SUCCESS;
}