+ assert (val2 != NULL);
+ tmp = gsl_matrix_get (cov->m, row, col);
+ gsl_matrix_set (cov->m, row, col, (val2->f - mean) * x + tmp);
+ gsl_matrix_set (cov->m, col, row, (val2->f - mean) * x + tmp);
+}
+static void
+column_iterate (struct design_matrix *cov, const struct variable *v,
+ double ssize, double x, const union value *val1, size_t row)
+{
+ size_t col;
+ size_t i;
+ double y;
+ double tmp;
+ const union value *tmp_val;
+
+ col = design_matrix_var_to_column (cov, v);
+ for (i = 0; i < cat_get_n_categories (v) - 1; i++)