test_isomap.py 文件源码

def test_isomap_simple_grid():
    # Isomap should preserve distances when all neighbors are used
    N_per_side = 5
    Npts = N_per_side ** 2
    n_neighbors = Npts - 1

    # grid of equidistant points in 2D, n_components = n_dim
    X = np.array(list(product(range(N_per_side), repeat=2)))

    # distances from each point to all others
    G = neighbors.kneighbors_graph(X, n_neighbors,
                                   mode='distance').toarray()

    for eigen_solver in eigen_solvers:
        for path_method in path_methods:
            clf = manifold.Isomap(n_neighbors=n_neighbors, n_components=2,
                                  eigen_solver=eigen_solver,
                                  path_method=path_method)
            clf.fit(X)

            G_iso = neighbors.kneighbors_graph(clf.embedding_,
                                               n_neighbors,
                                               mode='distance').toarray()
            assert_array_almost_equal(G, G_iso)