From 9b4be76534ceb66e6fbbb3d7790eec982e84fec8 Mon Sep 17 00:00:00 2001
From: Olivier Grisel <olivier.grisel@ensta.org>
Date: Wed, 2 May 2012 04:24:54 +0200
Subject: [PATCH] FIX #807: non regression test for KPCA on make_circles
dataset
---
.../decomposition/tests/test_kernel_pca.py | 29 ++++++++++++++++++-
sklearn/utils/testing.py | 5 ++++
2 files changed, 33 insertions(+), 1 deletion(-)
diff --git a/sklearn/decomposition/tests/test_kernel_pca.py b/sklearn/decomposition/tests/test_kernel_pca.py
index e0ef36a29b..e9a680b7c1 100644
--- a/sklearn/decomposition/tests/test_kernel_pca.py
+++ b/sklearn/decomposition/tests/test_kernel_pca.py
@@ -5,7 +5,11 @@ from numpy.testing import assert_array_almost_equal
from nose.tools import assert_equal
from nose.tools import assert_raises
-from .. import PCA, KernelPCA
+from sklearn.decomposition import PCA, KernelPCA
+from sklearn.datasets import make_circles
+from sklearn.linear_model import Perceptron
+from sklearn.cross_validation import cross_val_score
+from sklearn.utils.testing import assert_lower
def test_kernel_pca():
@@ -114,6 +118,29 @@ def test_kernel_pca_invalid_kernel():
assert_raises(ValueError, kpca.fit, X_fit)
+def test_nested_circles():
+ """Test the linear separability of the first 2D KPCA transform"""
+ X, y = make_circles(n_samples=400, factor=.3, noise=.05,
+ random_state=0)
+
+ # 2D nested circles are not linearly separable
+ train_score = Perceptron().fit(X, y).score(X, y)
+ assert_lower(train_score, 0.8)
+
+ # Project the circles data into the first 2 components of a RBF Kernel
+ # PCA model.
+ # Not that the gamma value is data dependent. If this test breaks
+ # and the gamma value has to be updated, the Kernel PCA example will
+ # have to be updated too.
+ kpca = KernelPCA(kernel="rbf", n_components=2,
+ fit_inverse_transform=True, gamma=10.)
+ X_kpca = kpca.fit_transform(X)
+
+ # The data is perfectly linearly separable in that space
+ train_score = Perceptron().fit(X_kpca, y).score(X_kpca, y)
+ assert_equal(train_score, 1.0)
+
+
if __name__ == '__main__':
import nose
nose.run(argv=['', __file__])
diff --git a/sklearn/utils/testing.py b/sklearn/utils/testing.py
index 2e9ba61658..96d1a13811 100644
--- a/sklearn/utils/testing.py
+++ b/sklearn/utils/testing.py
@@ -22,6 +22,11 @@ except ImportError:
assert_false(x in container, msg="%r in %r" % (x, container))
+def assert_lower(a, b):
+ message = "%r is not lower than %r" % (a, b)
+ assert a < b, message
+
+
def fake_mldata_cache(columns_dict, dataname, matfile, ordering=None):
"""Create a fake mldata data set in the cache_path.
--
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