def kmeans_clustering(self, numc, X=None, npcs=15):
        """Performs k-means clustering.

        Parameters
        ----------
        numc - int
            Number of clusters

        npcs - int, optional, default 15
            Number of principal components to use as inpute for k-means
            clustering.

        """

        from sklearn.cluster import KMeans
        if X is None:
            D_sub = self.adata.uns['X_processed']
            X = (
                D_sub -
                D_sub.mean(0)).dot(
                self.adata.uns['pca_obj'].components_[
                    :npcs,
                    :].T)
            save = True
        else:
            save = False

        cl = KMeans(n_clusters=numc).fit_predict(Normalizer().fit_transform(X))

        if save:
            self.adata.obs['kmeans_clusters'] = pd.Categorical(cl)
        else:
            return cl