Vehicle-Anti-Theft-Face-Rec.../venv/Lib/site-packages/sklearn/cluster/tests/test_dbscan.py

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2020-11-12 16:05:57 +00:00
"""
Tests for DBSCAN clustering algorithm
"""
import pickle
import numpy as np
from scipy.spatial import distance
from scipy import sparse
import pytest
from sklearn.utils._testing import assert_array_equal
from sklearn.neighbors import NearestNeighbors
from sklearn.cluster import DBSCAN
from sklearn.cluster import dbscan
from sklearn.cluster.tests.common import generate_clustered_data
from sklearn.metrics.pairwise import pairwise_distances
n_clusters = 3
X = generate_clustered_data(n_clusters=n_clusters)
def test_dbscan_similarity():
# Tests the DBSCAN algorithm with a similarity array.
# Parameters chosen specifically for this task.
eps = 0.15
min_samples = 10
# Compute similarities
D = distance.squareform(distance.pdist(X))
D /= np.max(D)
# Compute DBSCAN
core_samples, labels = dbscan(D, metric="precomputed", eps=eps,
min_samples=min_samples)
# number of clusters, ignoring noise if present
n_clusters_1 = len(set(labels)) - (1 if -1 in labels else 0)
assert n_clusters_1 == n_clusters
db = DBSCAN(metric="precomputed", eps=eps, min_samples=min_samples)
labels = db.fit(D).labels_
n_clusters_2 = len(set(labels)) - int(-1 in labels)
assert n_clusters_2 == n_clusters
def test_dbscan_feature():
# Tests the DBSCAN algorithm with a feature vector array.
# Parameters chosen specifically for this task.
# Different eps to other test, because distance is not normalised.
eps = 0.8
min_samples = 10
metric = 'euclidean'
# Compute DBSCAN
# parameters chosen for task
core_samples, labels = dbscan(X, metric=metric, eps=eps,
min_samples=min_samples)
# number of clusters, ignoring noise if present
n_clusters_1 = len(set(labels)) - int(-1 in labels)
assert n_clusters_1 == n_clusters
db = DBSCAN(metric=metric, eps=eps, min_samples=min_samples)
labels = db.fit(X).labels_
n_clusters_2 = len(set(labels)) - int(-1 in labels)
assert n_clusters_2 == n_clusters
def test_dbscan_sparse():
core_sparse, labels_sparse = dbscan(sparse.lil_matrix(X), eps=.8,
min_samples=10)
core_dense, labels_dense = dbscan(X, eps=.8, min_samples=10)
assert_array_equal(core_dense, core_sparse)
assert_array_equal(labels_dense, labels_sparse)
@pytest.mark.parametrize('include_self', [False, True])
def test_dbscan_sparse_precomputed(include_self):
D = pairwise_distances(X)
nn = NearestNeighbors(radius=.9).fit(X)
X_ = X if include_self else None
D_sparse = nn.radius_neighbors_graph(X=X_, mode='distance')
# Ensure it is sparse not merely on diagonals:
assert D_sparse.nnz < D.shape[0] * (D.shape[0] - 1)
core_sparse, labels_sparse = dbscan(D_sparse,
eps=.8,
min_samples=10,
metric='precomputed')
core_dense, labels_dense = dbscan(D, eps=.8, min_samples=10,
metric='precomputed')
assert_array_equal(core_dense, core_sparse)
assert_array_equal(labels_dense, labels_sparse)
def test_dbscan_sparse_precomputed_different_eps():
# test that precomputed neighbors graph is filtered if computed with
# a radius larger than DBSCAN's eps.
lower_eps = 0.2
nn = NearestNeighbors(radius=lower_eps).fit(X)
D_sparse = nn.radius_neighbors_graph(X, mode='distance')
dbscan_lower = dbscan(D_sparse, eps=lower_eps, metric='precomputed')
higher_eps = lower_eps + 0.7
nn = NearestNeighbors(radius=higher_eps).fit(X)
D_sparse = nn.radius_neighbors_graph(X, mode='distance')
dbscan_higher = dbscan(D_sparse, eps=lower_eps, metric='precomputed')
assert_array_equal(dbscan_lower[0], dbscan_higher[0])
assert_array_equal(dbscan_lower[1], dbscan_higher[1])
@pytest.mark.parametrize('use_sparse', [True, False])
@pytest.mark.parametrize('metric', ['precomputed', 'minkowski'])
def test_dbscan_input_not_modified(use_sparse, metric):
# test that the input is not modified by dbscan
X = np.random.RandomState(0).rand(10, 10)
X = sparse.csr_matrix(X) if use_sparse else X
X_copy = X.copy()
dbscan(X, metric=metric)
if use_sparse:
assert_array_equal(X.toarray(), X_copy.toarray())
else:
assert_array_equal(X, X_copy)
def test_dbscan_no_core_samples():
rng = np.random.RandomState(0)
X = rng.rand(40, 10)
X[X < .8] = 0
for X_ in [X, sparse.csr_matrix(X)]:
db = DBSCAN(min_samples=6).fit(X_)
assert_array_equal(db.components_, np.empty((0, X_.shape[1])))
assert_array_equal(db.labels_, -1)
assert db.core_sample_indices_.shape == (0,)
def test_dbscan_callable():
# Tests the DBSCAN algorithm with a callable metric.
# Parameters chosen specifically for this task.
# Different eps to other test, because distance is not normalised.
eps = 0.8
min_samples = 10
# metric is the function reference, not the string key.
metric = distance.euclidean
# Compute DBSCAN
# parameters chosen for task
core_samples, labels = dbscan(X, metric=metric, eps=eps,
min_samples=min_samples,
algorithm='ball_tree')
# number of clusters, ignoring noise if present
n_clusters_1 = len(set(labels)) - int(-1 in labels)
assert n_clusters_1 == n_clusters
db = DBSCAN(metric=metric, eps=eps, min_samples=min_samples,
algorithm='ball_tree')
labels = db.fit(X).labels_
n_clusters_2 = len(set(labels)) - int(-1 in labels)
assert n_clusters_2 == n_clusters
def test_dbscan_metric_params():
# Tests that DBSCAN works with the metrics_params argument.
eps = 0.8
min_samples = 10
p = 1
# Compute DBSCAN with metric_params arg
db = DBSCAN(metric='minkowski', metric_params={'p': p}, eps=eps,
min_samples=min_samples, algorithm='ball_tree').fit(X)
core_sample_1, labels_1 = db.core_sample_indices_, db.labels_
# Test that sample labels are the same as passing Minkowski 'p' directly
db = DBSCAN(metric='minkowski', eps=eps, min_samples=min_samples,
algorithm='ball_tree', p=p).fit(X)
core_sample_2, labels_2 = db.core_sample_indices_, db.labels_
assert_array_equal(core_sample_1, core_sample_2)
assert_array_equal(labels_1, labels_2)
# Minkowski with p=1 should be equivalent to Manhattan distance
db = DBSCAN(metric='manhattan', eps=eps, min_samples=min_samples,
algorithm='ball_tree').fit(X)
core_sample_3, labels_3 = db.core_sample_indices_, db.labels_
assert_array_equal(core_sample_1, core_sample_3)
assert_array_equal(labels_1, labels_3)
def test_dbscan_balltree():
# Tests the DBSCAN algorithm with balltree for neighbor calculation.
eps = 0.8
min_samples = 10
D = pairwise_distances(X)
core_samples, labels = dbscan(D, metric="precomputed", eps=eps,
min_samples=min_samples)
# number of clusters, ignoring noise if present
n_clusters_1 = len(set(labels)) - int(-1 in labels)
assert n_clusters_1 == n_clusters
db = DBSCAN(p=2.0, eps=eps, min_samples=min_samples, algorithm='ball_tree')
labels = db.fit(X).labels_
n_clusters_2 = len(set(labels)) - int(-1 in labels)
assert n_clusters_2 == n_clusters
db = DBSCAN(p=2.0, eps=eps, min_samples=min_samples, algorithm='kd_tree')
labels = db.fit(X).labels_
n_clusters_3 = len(set(labels)) - int(-1 in labels)
assert n_clusters_3 == n_clusters
db = DBSCAN(p=1.0, eps=eps, min_samples=min_samples, algorithm='ball_tree')
labels = db.fit(X).labels_
n_clusters_4 = len(set(labels)) - int(-1 in labels)
assert n_clusters_4 == n_clusters
db = DBSCAN(leaf_size=20, eps=eps, min_samples=min_samples,
algorithm='ball_tree')
labels = db.fit(X).labels_
n_clusters_5 = len(set(labels)) - int(-1 in labels)
assert n_clusters_5 == n_clusters
def test_input_validation():
# DBSCAN.fit should accept a list of lists.
X = [[1., 2.], [3., 4.]]
DBSCAN().fit(X) # must not raise exception
@pytest.mark.parametrize(
"args",
[{'eps': -1.0}, {'algorithm': 'blah'}, {'metric': 'blah'},
{'leaf_size': -1}, {'p': -1}]
)
def test_dbscan_badargs(args):
# Test bad argument values: these should all raise ValueErrors
with pytest.raises(ValueError):
dbscan(X, **args)
def test_pickle():
obj = DBSCAN()
s = pickle.dumps(obj)
assert type(pickle.loads(s)) == obj.__class__
def test_boundaries():
# ensure min_samples is inclusive of core point
core, _ = dbscan([[0], [1]], eps=2, min_samples=2)
assert 0 in core
# ensure eps is inclusive of circumference
core, _ = dbscan([[0], [1], [1]], eps=1, min_samples=2)
assert 0 in core
core, _ = dbscan([[0], [1], [1]], eps=.99, min_samples=2)
assert 0 not in core
def test_weighted_dbscan():
# ensure sample_weight is validated
with pytest.raises(ValueError):
dbscan([[0], [1]], sample_weight=[2])
with pytest.raises(ValueError):
dbscan([[0], [1]], sample_weight=[2, 3, 4])
# ensure sample_weight has an effect
assert_array_equal([], dbscan([[0], [1]], sample_weight=None,
min_samples=6)[0])
assert_array_equal([], dbscan([[0], [1]], sample_weight=[5, 5],
min_samples=6)[0])
assert_array_equal([0], dbscan([[0], [1]], sample_weight=[6, 5],
min_samples=6)[0])
assert_array_equal([0, 1], dbscan([[0], [1]], sample_weight=[6, 6],
min_samples=6)[0])
# points within eps of each other:
assert_array_equal([0, 1], dbscan([[0], [1]], eps=1.5,
sample_weight=[5, 1], min_samples=6)[0])
# and effect of non-positive and non-integer sample_weight:
assert_array_equal([], dbscan([[0], [1]], sample_weight=[5, 0],
eps=1.5, min_samples=6)[0])
assert_array_equal([0, 1], dbscan([[0], [1]], sample_weight=[5.9, 0.1],
eps=1.5, min_samples=6)[0])
assert_array_equal([0, 1], dbscan([[0], [1]], sample_weight=[6, 0],
eps=1.5, min_samples=6)[0])
assert_array_equal([], dbscan([[0], [1]], sample_weight=[6, -1],
eps=1.5, min_samples=6)[0])
# for non-negative sample_weight, cores should be identical to repetition
rng = np.random.RandomState(42)
sample_weight = rng.randint(0, 5, X.shape[0])
core1, label1 = dbscan(X, sample_weight=sample_weight)
assert len(label1) == len(X)
X_repeated = np.repeat(X, sample_weight, axis=0)
core_repeated, label_repeated = dbscan(X_repeated)
core_repeated_mask = np.zeros(X_repeated.shape[0], dtype=bool)
core_repeated_mask[core_repeated] = True
core_mask = np.zeros(X.shape[0], dtype=bool)
core_mask[core1] = True
assert_array_equal(np.repeat(core_mask, sample_weight), core_repeated_mask)
# sample_weight should work with precomputed distance matrix
D = pairwise_distances(X)
core3, label3 = dbscan(D, sample_weight=sample_weight,
metric='precomputed')
assert_array_equal(core1, core3)
assert_array_equal(label1, label3)
# sample_weight should work with estimator
est = DBSCAN().fit(X, sample_weight=sample_weight)
core4 = est.core_sample_indices_
label4 = est.labels_
assert_array_equal(core1, core4)
assert_array_equal(label1, label4)
est = DBSCAN()
label5 = est.fit_predict(X, sample_weight=sample_weight)
core5 = est.core_sample_indices_
assert_array_equal(core1, core5)
assert_array_equal(label1, label5)
assert_array_equal(label1, est.labels_)
@pytest.mark.parametrize('algorithm', ['brute', 'kd_tree', 'ball_tree'])
def test_dbscan_core_samples_toy(algorithm):
X = [[0], [2], [3], [4], [6], [8], [10]]
n_samples = len(X)
# Degenerate case: every sample is a core sample, either with its own
# cluster or including other close core samples.
core_samples, labels = dbscan(X, algorithm=algorithm, eps=1,
min_samples=1)
assert_array_equal(core_samples, np.arange(n_samples))
assert_array_equal(labels, [0, 1, 1, 1, 2, 3, 4])
# With eps=1 and min_samples=2 only the 3 samples from the denser area
# are core samples. All other points are isolated and considered noise.
core_samples, labels = dbscan(X, algorithm=algorithm, eps=1,
min_samples=2)
assert_array_equal(core_samples, [1, 2, 3])
assert_array_equal(labels, [-1, 0, 0, 0, -1, -1, -1])
# Only the sample in the middle of the dense area is core. Its two
# neighbors are edge samples. Remaining samples are noise.
core_samples, labels = dbscan(X, algorithm=algorithm, eps=1,
min_samples=3)
assert_array_equal(core_samples, [2])
assert_array_equal(labels, [-1, 0, 0, 0, -1, -1, -1])
# It's no longer possible to extract core samples with eps=1:
# everything is noise.
core_samples, labels = dbscan(X, algorithm=algorithm, eps=1,
min_samples=4)
assert_array_equal(core_samples, [])
assert_array_equal(labels, np.full(n_samples, -1.))
def test_dbscan_precomputed_metric_with_degenerate_input_arrays():
# see https://github.com/scikit-learn/scikit-learn/issues/4641 for
# more details
X = np.eye(10)
labels = DBSCAN(eps=0.5, metric='precomputed').fit(X).labels_
assert len(set(labels)) == 1
X = np.zeros((10, 10))
labels = DBSCAN(eps=0.5, metric='precomputed').fit(X).labels_
assert len(set(labels)) == 1
def test_dbscan_precomputed_metric_with_initial_rows_zero():
# sample matrix with initial two row all zero
ar = np.array([
[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
[0.0, 0.0, 0.0, 0.0, 0.1, 0.0, 0.0],
[0.0, 0.0, 0.0, 0.0, 0.1, 0.0, 0.0],
[0.0, 0.0, 0.1, 0.1, 0.0, 0.0, 0.3],
[0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.1],
[0.0, 0.0, 0.0, 0.0, 0.3, 0.1, 0.0]
])
matrix = sparse.csr_matrix(ar)
labels = DBSCAN(eps=0.2, metric='precomputed',
min_samples=2).fit(matrix).labels_
assert_array_equal(labels, [-1, -1, 0, 0, 0, 1, 1])