fix bug 19819

diff --git a/src/language/stats/ChangeLog b/src/language/stats/ChangeLog
index ac368fd0ec569c84c3ac8acc60ca85f82e0fd904..55c4a8e3f31511cb45ebb28646fa091cfbbf755e 100644 (file)
--- a/src/language/stats/ChangeLog
+++ b/src/language/stats/ChangeLog
@@ -1,3 +1,8 @@
+2007-08-15  Jason Stover  <jhs@wonko.gcsu.edu>
+
+       * regression.q (identify_indep_vars): Print an error if dependent
+       and independent variables are the same. Fixes bug 19819.
+
 2007-08-12  Ben Pfaff  <blp@gnu.org>
 
        * flip.c: Drop use of dict_get_compacted_dict_index_to_case_index

diff --git a/src/language/stats/regression.q b/src/language/stats/regression.q
index d5008b5681178b5890584ca08b20ee04169a6e31..c6fddb90df5e585dc053e8cc3b37205be2a6f6a0 100644 (file)
--- a/src/language/stats/regression.q
+++ b/src/language/stats/regression.q
@@ -1021,7 +1021,17 @@ identify_indep_vars (const struct variable **indep_vars,
   for (i = 0; i < n_variables; i++)
     if (!is_depvar (i, depvar))
       indep_vars[n_indep_vars++] = v_variables[i];
-
+  if ((n_indep_vars < 2) && is_depvar (0, depvar))
+    {
+      /*
+       There is only one independent variable, and it is the same
+       as the dependent variable. Print a warning and continue.
+       */
+      msg (SE,
+          gettext ("The dependent variable is equal to the independent variable. The least sequares line is therefore Y=X. Standard errors and related statistics may be meaningless."));
+      n_indep_vars = 1;
+      indep_vars[0] = v_variables[0];
+    }
   return n_indep_vars;
 }
 
@@ -1036,6 +1046,9 @@ prepare_categories (struct casereader *input,
   struct ccase c;
   size_t i;
 
+  assert (vars != NULL);
+  assert (mom != NULL);
+
   for (i = 0; i < n_vars; i++)
     if (var_is_alpha (vars[i]))
       cat_stored_values_create (vars[i]);
@@ -1163,7 +1176,6 @@ run_regression (struct casereader *input, struct cmd_regression *cmd,
 
       dep_var = cmd->v_dependent[k];
       n_indep = identify_indep_vars (indep_vars, dep_var);
-
       reader = casereader_clone (input);
       reader = casereader_create_filter_missing (reader, indep_vars, n_indep,
                                                 MV_ANY, NULL);