Functions to handle coefficient-to-variable/value matching

[pspp-builds.git] / lib / linreg / coefficient.c

diff --git a/lib/linreg/coefficient.c b/lib/linreg/coefficient.c
new file mode 100644 (file)
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+++ b/lib/linreg/coefficient.c
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+/* lib/linreg/coefficient.c
+
+   Copyright (C) 2005 Free Software Foundation, Inc.
+   Written by Jason H Stover.
+
+   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
+   the Free Software Foundation; either version 2 of the License, or (at
+   your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+   02111-1307, USA.
+ */
+
+/*
+  Accessor functions for matching coefficients and variables.
+ */
+#include <assert.h>
+#include "pspp_linreg.h"
+#include <gl/xalloc.h>
+
+
+struct varinfo
+{
+  const struct variable *v; /* Variable associated with this
+                              coefficient. Note this variable may not
+                              be unique. In other words, a
+                              coefficient structure may have other
+                              v_info's, each with its own variable.
+                            */
+  const union value *val; /* Value of the variable v which this
+                            varinfo refers to. This member is relevant
+                            only to categorical variables.
+                         */
+};
+
+void pspp_linreg_coeff_free (struct pspp_linreg_coeff *c)
+{
+  free (c->v_info);
+  free (c);
+}
+
+/*
+  Initialize the variable and value pointers inside the
+  coefficient structures for the linear model.
+ */
+void
+pspp_linreg_coeff_init (pspp_linreg_cache *c, struct design_matrix *X)
+{
+  size_t i;
+  size_t j;
+  int n_vals = 1;
+  struct pspp_linreg_coeff *coeff;
+  
+  c->coeff = xnmalloc (X->m->size2 + 1, sizeof (*c->coeff));
+  for (i = 0; i < X->m->size2; i++)
+    {
+      j = i + 1;               /* The first coefficient is the intercept. */
+      coeff = c->coeff + j;
+      coeff->n_vars = n_vals; /* Currently, no procedures allow interactions.
+                                This will have to change when procedures that
+                                allow interaction terms are written.
+                             */
+      coeff->v_info = xnmalloc (coeff->n_vars, sizeof (*coeff->v_info));
+      assert (coeff->v_info != NULL);
+      coeff->v_info->v = (const struct variable *) design_matrix_col_to_var (X, i);
+      
+      if (coeff->v_info->v->type == ALPHA)
+       {
+         size_t k;
+         k = design_matrix_var_to_column (X, coeff->v_info->v);
+         assert (k <= i);
+         k = i - k;
+         coeff->v_info->val = cat_subscript_to_value (k, (struct variable *) coeff->v_info->v);
+       }
+    }
+}
+void
+pspp_linreg_coeff_set_estimate (struct pspp_linreg_coeff *c,
+                               double estimate)
+{
+  c->estimate = estimate;
+}
+void
+pspp_linreg_coeff_set_std_err (struct pspp_linreg_coeff *c,
+                              double std_err)
+{
+  c->std_err = std_err;
+}
+/*
+  How many variables are associated with this coefficient?
+ */
+int
+pspp_linreg_coeff_get_n_vars (struct pspp_linreg_coeff *c)
+{
+  return c->n_vars;
+}                            
+/*
+  Which variable does this coefficient match?
+ */
+const struct variable *
+pspp_linreg_coeff_get_var (struct pspp_linreg_coeff *c, int i)
+{
+  assert (i < c->n_vars);
+  return (c->v_info + i)->v;
+}
+/* 
+   Which value is associated with this coefficient/variable comination? 
+*/
+const union value *
+pspp_linreg_coeff_get_value (struct pspp_linreg_coeff *c,
+                            const struct variable *v)
+{
+  int i = 0;
+  const struct variable *candidate;
+
+  while (i < c->n_vars)
+    {
+      candidate = pspp_linreg_coeff_get_var (c, i);
+      if (v->index == candidate->index)
+       {
+         return (c->v_info + i)->val;
+       }
+      i++;
+    }
+  return NULL;
+}