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from itertools import product
import numpy as np
from numpy.testing import (assert_almost_equal, assert_array_almost_equal,
assert_equal)
from sklearn import datasets
from sklearn import manifold
from sklearn import neighbors
from sklearn import pipeline
from sklearn import preprocessing
from sklearn.utils.testing import assert_less
from scipy.sparse import rand as sparse_rand
eigen_solvers = ['auto', 'dense', 'arpack']
path_methods = ['auto', 'FW', 'D']
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)
def test_isomap_reconstruction_error():
# Same setup as in test_isomap_simple_grid, with an added dimension
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)))
# add noise in a third dimension
rng = np.random.RandomState(0)
noise = 0.1 * rng.randn(Npts, 1)
X = np.concatenate((X, noise), 1)
# compute input kernel
G = neighbors.kneighbors_graph(X, n_neighbors,
mode='distance').toarray()
centerer = preprocessing.KernelCenterer()
K = centerer.fit_transform(-0.5 * G ** 2)
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)
# compute output kernel
G_iso = neighbors.kneighbors_graph(clf.embedding_,
n_neighbors,
mode='distance').toarray()
K_iso = centerer.fit_transform(-0.5 * G_iso ** 2)
# make sure error agrees
reconstruction_error = np.linalg.norm(K - K_iso) / Npts
assert_almost_equal(reconstruction_error,
clf.reconstruction_error())
def test_transform():
n_samples = 200
n_components = 10
noise_scale = 0.01
# Create S-curve dataset
X, y = datasets.samples_generator.make_s_curve(n_samples, random_state=0)
# Compute isomap embedding
iso = manifold.Isomap(n_components, 2)
X_iso = iso.fit_transform(X)
# Re-embed a noisy version of the points
rng = np.random.RandomState(0)
noise = noise_scale * rng.randn(*X.shape)
X_iso2 = iso.transform(X + noise)
# Make sure the rms error on re-embedding is comparable to noise_scale
assert_less(np.sqrt(np.mean((X_iso - X_iso2) ** 2)), 2 * noise_scale)
def test_pipeline():
# check that Isomap works fine as a transformer in a Pipeline
# only checks that no error is raised.
# TODO check that it actually does something useful
X, y = datasets.make_blobs(random_state=0)
clf = pipeline.Pipeline(
[('isomap', manifold.Isomap()),
('clf', neighbors.KNeighborsClassifier())])
clf.fit(X, y)
assert_less(.9, clf.score(X, y))
def test_isomap_clone_bug():
# regression test for bug reported in #6062
model = manifold.Isomap()
for n_neighbors in [10, 15, 20]:
model.set_params(n_neighbors=n_neighbors)
model.fit(np.random.rand(50, 2))
assert_equal(model.nbrs_.n_neighbors,
n_neighbors)
def test_sparse_input():
X = sparse_rand(100, 3, density=0.1, format='csr')
# Should not error
for eigen_solver in eigen_solvers:
for path_method in path_methods:
clf = manifold.Isomap(n_components=2,
eigen_solver=eigen_solver,
path_method=path_method)
clf.fit(X)
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