store intercept in proper place when using QR method

[pspp-builds.git] / src / math / linreg / linreg.c

diff --git a/src/math/linreg/linreg.c b/src/math/linreg/linreg.c
index 4fc3b20a74d55bb5d284e5269764edf861312eed..0782c36fc3df82aae30d00c5f88fbd5f89aa3ad7 100644 (file)
--- a/src/math/linreg/linreg.c
+++ b/src/math/linreg/linreg.c
@@ -1,5 +1,5 @@
 /* PSPP - a program for statistical analysis.
-   Copyright (C) 2005 Free Software Foundation, Inc. Written by Jason H. Stover.
+   Copyright (C) 2005 Free Software Foundation, Inc. 
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -94,9 +94,9 @@ int
 pspp_linreg_get_vars (const void *c_, const struct variable **v)
 {
   const pspp_linreg_cache *c = c_;
-  struct pspp_coeff *coef = NULL;
   const struct variable *tmp;
   int i;
+  int j;
   int result = 0;
 
   /*
@@ -107,15 +107,9 @@ pspp_linreg_get_vars (const void *c_, const struct variable **v)
     {
       v[i] = NULL;
     }
-  /*
-     Start at c->coeff[1] to avoid the intercept.
-   */
-  v[result] = pspp_coeff_get_var (c->coeff[1], 0);
-  result = (v[result] == NULL) ? 0 : 1;
-
-  for (coef = c->coeff[2]; coef < c->coeff[c->n_coeffs]; coef++)
+  for (j = 0; j < c->n_coeffs; j++)
     {
-      tmp = pspp_coeff_get_var (coef, 0);
+      tmp = pspp_coeff_get_var (c->coeff[j], 0);
       assert (tmp != NULL);
       /* Repeated variables are likely to bunch together, at the end
          of the array. */
@@ -246,9 +240,9 @@ pspp_linreg (const gsl_vector * Y, const gsl_matrix * X,
   cache->dft = cache->n_obs - 1;
   cache->dfm = cache->n_indeps;
   cache->dfe = cache->dft - cache->dfm;
-  cache->n_coeffs = X->size2 + 1;      /* Adjust this later to allow for
-                                          regression through the origin.
-                                        */
+  cache->n_coeffs = X->size2;
+  cache->intercept = 0.0;
+
   if (cache->method == PSPP_LINREG_SWEEP)
     {
       gsl_matrix *sw;
@@ -322,7 +316,7 @@ pspp_linreg (const gsl_vector * Y, const gsl_matrix * X,
       for (i = 0; i < cache->n_indeps; i++)
        {
          tmp = gsl_matrix_get (sw, i, cache->n_indeps);
-         cache->coeff[i + 1]->estimate = tmp;
+         cache->coeff[i]->estimate = tmp;
          m -= tmp * gsl_vector_get (cache->indep_means, i);
        }
       /*
@@ -358,7 +352,7 @@ pspp_linreg (const gsl_vector * Y, const gsl_matrix * X,
            }
          gsl_matrix_set (cache->cov, 0, 0, tmp);
 
-         cache->coeff[0]->estimate = m;
+         cache->intercept = m;
        }
       else
        {
@@ -403,10 +397,11 @@ pspp_linreg (const gsl_vector * Y, const gsl_matrix * X,
       wk = gsl_multifit_linear_alloc (design->size1, design->size2);
       rc = gsl_multifit_linear (design, Y, param_estimates,
                                cache->cov, &(cache->sse), wk);
-      for (i = 0; i < cache->n_coeffs; i++)
+      for (i = 1; i < cache->n_coeffs; i++)
        {
          cache->coeff[i]->estimate = gsl_vector_get (param_estimates, i);
        }
+      cache->intercept = gsl_vector_get (param_estimates, 0);
       if (rc == GSL_SUCCESS)
        {
          gsl_multifit_linear_free (wk);