clusters a given matrix by into specified number of clusters according to given metric

def _make_clusters(self, matrix, num_clusters_per_roi, metric):
        """clusters a given matrix by into specified number of clusters according to given metric"""

        from scipy.cluster.hierarchy import fclusterdata

        # maxclust needed to ensure t is interpreted as # clusters in heirarchical clustering
        group_ids = fclusterdata(matrix, metric=metric, t=num_clusters_per_roi,
                                 criterion='maxclust')
        group_set = np.unique(group_ids)
        clusters = [
            self._summary_func(matrix[group_ids == group, :], axis=0, keepdims=True)
            for group in group_set]

        return np.vstack(clusters).squeeze()