NAG Library Manual, Mark 27.2
Interfaces:  FL   CL   CPP   AD 

NAG CL Interface Introduction
Example description
/* nag_mv_discrim_mahal (g03dbc) Example Program.
 *
 * Copyright 2021 Numerical Algorithms Group.
 *
 * Mark 27.2, 2021.
 *
 */

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

#define D(I, J) d[(I)*tdd + J]
#define X(I, J) x[(I)*tdx + J]

int main(void) {

  Integer i, j, m, n, ng, nobs, nvar, tdd, tdgmean, tdx;
  Integer exit_status = 0, *ing = 0, *isx = 0, *nig = 0;
  char nag_enum_arg[40];
  double df, sig, stat;
  double *d = 0, *det = 0, *gc = 0, *gmean = 0, *wt = 0;
  double *wtptr = 0, *x = 0;
  Nag_GroupCovars equal;
  Nag_Boolean weight;
  NagError fail;

  INIT_FAIL(fail);

  printf("nag_mv_discrim_mahal (g03dbc) Example Program Results\n\n");

  /* Skip headings in data file */
  scanf("%*[^\n]");
  scanf("%" NAG_IFMT "", &n);
  scanf("%" NAG_IFMT "", &m);
  scanf("%" NAG_IFMT "", &nvar);
  scanf("%" NAG_IFMT "", &ng);
  scanf("%39s", nag_enum_arg);
  /* nag_enum_name_to_value (x04nac).
   * Converts NAG enum member name to value
   */
  weight = (Nag_Boolean)nag_enum_name_to_value(nag_enum_arg);

  if (n >= 1 && nvar >= 1 && m >= nvar && ng >= 2) {
    if (!(det = NAG_ALLOC(ng, double)) ||
        !(gc = NAG_ALLOC((ng + 1) * nvar * (nvar + 1) / 2, double)) ||
        !(gmean = NAG_ALLOC(ng * nvar, double)) ||
        !(wt = NAG_ALLOC(n, double)) || !(x = NAG_ALLOC(n * m, double)) ||
        !(ing = NAG_ALLOC(n, Integer)) || !(isx = NAG_ALLOC(m, Integer)) ||
        !(nig = NAG_ALLOC(ng, Integer))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
    tdgmean = nvar;
    tdx = m;
  } else {
    printf("Invalid n or nvar or m or ng.\n");
    exit_status = 1;
    return exit_status;
  }
  if (weight) {
    for (i = 0; i < n; ++i) {
      for (j = 0; j < m; ++j)
        scanf("%lf", &X(i, j));
      scanf("%" NAG_IFMT "", &ing[i]);
      scanf("%lf", &wt[i]);
    }
    wtptr = wt;
  } else {
    for (i = 0; i < n; ++i) {
      for (j = 0; j < m; ++j)
        scanf("%lf", &X(i, j));
      scanf("%" NAG_IFMT "", &ing[i]);
    }
  }
  for (j = 0; j < m; ++j)
    scanf("%" NAG_IFMT "", &isx[j]);
  /* nag_mv_discrim (g03dac).
   * Test for equality of within-group covariance matrices
   */
  nag_mv_discrim(n, m, x, tdx, isx, nvar, ing, ng, wtptr, nig, gmean, tdgmean,
                 det, gc, &stat, &df, &sig, &fail);
  if (fail.code != NE_NOERROR) {
    printf("Error from nag_mv_discrim (g03dac).\n%s\n", fail.message);
    exit_status = 1;
    goto END;
  }
  scanf("%" NAG_IFMT "", &nobs);
  scanf("%39s", nag_enum_arg);
  equal = (Nag_GroupCovars)nag_enum_name_to_value(nag_enum_arg);
  if (nobs >= 1) {
    if (!(d = NAG_ALLOC(nobs * ng, double))) {
      printf("Allocation failure\n");
      exit_status = -1;
      goto END;
    }
    tdd = ng;

    for (i = 0; i < nobs; ++i) {
      for (j = 0; j < m; ++j)
        scanf("%lf", &X(i, j));
    }

    /* nag_mv_discrim_mahal (g03dbc).
     * Mahalanobis squared distances, following nag_mv_discrim
     * (g03dac)
     */
    nag_mv_discrim_mahal(equal, Nag_SamplePoints, nvar, ng, gmean, tdgmean, gc,
                         nobs, m, isx, x, tdx, d, tdd, &fail);
    if (fail.code != NE_NOERROR) {
      printf("Error from nag_mv_discrim_mahal (g03dbc).\n%s\n", fail.message);
      exit_status = 1;
      goto END;
    }
    printf("\n   Obs          Distances\n\n");
    for (i = 0; i < nobs; ++i) {
      printf(" %3" NAG_IFMT "", i + 1);
      for (j = 0; j < ng; ++j)
        printf("%10.3f", D(i, j));
      printf("\n");
    }
  }

END:
  NAG_FREE(d);
  NAG_FREE(det);
  NAG_FREE(gc);
  NAG_FREE(gmean);
  NAG_FREE(wt);
  NAG_FREE(x);
  NAG_FREE(ing);
  NAG_FREE(isx);
  NAG_FREE(nig);

  return exit_status;
}