code: private double[][] findBasis(Relation<V> database, ORCLUSCluster cluster, int dim) {
      PCAResult pcares = pca.processIds(cluster.objectIDs, database);
      final double[][] evs = pcares.getEigenvectors();
      return Arrays.copyOfRange(evs, evs.length - dim, evs.length);
    }
docs: Finds the basis of the subspace of dimensionality <code>dim</code> for the
  specified cluster.
  
  @param database the database to run the algorithm on
  @param cluster the cluster
  @param dim the dimensionality of the subspace
  @return matrix defining the basis of the subspace for the specified cluster