const struct variable *weight, enum mv_class exclude)
{
size_t i;
- struct covariance *cov = xmalloc (sizeof *cov);
+ struct covariance *cov = xzalloc (sizeof *cov);
cov->passes = 1;
cov->state = 0;
cov->n_cm = (n_vars * (n_vars - 1) ) / 2;
- cov->cm = xcalloc (sizeof *cov->cm, cov->n_cm);
+ if (cov->n_cm > 0)
+ cov->cm = xcalloc (sizeof *cov->cm, cov->n_cm);
cov->categoricals = NULL;
return cov;
return categoricals_get_binary_by_subscript (cov->categoricals, i - cov->n_vars, c);
}
+#if 0
void
dump_matrix (const gsl_matrix *m)
{
printf ("\n");
}
}
+#endif
/* Call this function for every case in the data set */
void
}
-
/*
Return a pointer to gsl_matrix containing the pairwise covariances.
The matrix remains owned by the COV object, and must not be freed.
}
}
+/*
+ Covariance computed without dividing by the sample size.
+ */
+static const gsl_matrix *
+covariance_calculate_double_pass_unnormalized (struct covariance *cov)
+{
+ size_t i, j;
+ for (i = 0 ; i < cov->dim; ++i)
+ {
+ for (j = 0 ; j < cov->dim; ++j)
+ {
+ int idx;
+ double *x = gsl_matrix_ptr (cov->moments[MOMENT_VARIANCE], i, j);
+
+ idx = cm_idx (cov, i, j);
+ if ( idx >= 0)
+ {
+ x = &cov->cm [idx];
+ }
+ }
+ }
+
+ return cm_to_gsl (cov);
+}
+
+static const gsl_matrix *
+covariance_calculate_single_pass_unnormalized (struct covariance *cov)
+{
+ size_t i, j;
+
+ for (i = 0 ; i < cov->dim; ++i)
+ {
+ for (j = 0 ; j < cov->dim; ++j)
+ {
+ double *x = gsl_matrix_ptr (cov->moments[MOMENT_VARIANCE], i, j);
+ *x -= pow2 (gsl_matrix_get (cov->moments[MOMENT_MEAN], i, j))
+ / gsl_matrix_get (cov->moments[MOMENT_NONE], i, j);
+ }
+ }
+ for ( j = 0 ; j < cov->dim - 1; ++j)
+ {
+ for (i = j + 1 ; i < cov->dim; ++i)
+ {
+ double *x = &cov->cm [cm_idx (cov, i, j)];
+
+ *x -=
+ gsl_matrix_get (cov->moments[MOMENT_MEAN], i, j)
+ *
+ gsl_matrix_get (cov->moments[MOMENT_MEAN], j, i)
+ / gsl_matrix_get (cov->moments[MOMENT_NONE], i, j);
+ }
+ }
+
+ return cm_to_gsl (cov);
+}
+
+
+/*
+ Return a pointer to gsl_matrix containing the pairwise covariances.
+ The matrix remains owned by the COV object, and must not be freed.
+ Call this function only after all data have been accumulated.
+*/
+const gsl_matrix *
+covariance_calculate_unnormalized (struct covariance *cov)
+{
+ assert ( cov->state > 0 );
+
+ switch (cov->passes)
+ {
+ case 1:
+ return covariance_calculate_single_pass_unnormalized (cov);
+ break;
+ case 2:
+ return covariance_calculate_double_pass_unnormalized (cov);
+ break;
+ default:
+ NOT_REACHED ();
+ }
+}
covariance_destroy (struct covariance *cov)
{
size_t i;
- free (cov->vars);
+
categoricals_destroy (cov->categoricals);
for (i = 0; i < n_MOMENTS; ++i)