.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "auto_examples/applications/plot_outlier_detection_wine.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code. or to run this example in your browser via Binder .. rst-class:: sphx-glr-example-title .. _sphx_glr_auto_examples_applications_plot_outlier_detection_wine.py: ==================================== Outlier detection on a real data set ==================================== This example illustrates the need for robust covariance estimation on a real data set. It is useful both for outlier detection and for a better understanding of the data structure. We selected two sets of two variables from the Wine data set as an illustration of what kind of analysis can be done with several outlier detection tools. For the purpose of visualization, we are working with two-dimensional examples, but one should be aware that things are not so trivial in high-dimension, as it will be pointed out. In both examples below, the main result is that the empirical covariance estimate, as a non-robust one, is highly influenced by the heterogeneous structure of the observations. Although the robust covariance estimate is able to focus on the main mode of the data distribution, it sticks to the assumption that the data should be Gaussian distributed, yielding some biased estimation of the data structure, but yet accurate to some extent. The One-Class SVM does not assume any parametric form of the data distribution and can therefore model the complex shape of the data much better. .. GENERATED FROM PYTHON SOURCE LINES 25-29 .. code-block:: Python # Authors: The scikit-learn developers # SPDX-License-Identifier: BSD-3-Clause .. GENERATED FROM PYTHON SOURCE LINES 30-40 First example ------------- The first example illustrates how the Minimum Covariance Determinant robust estimator can help concentrate on a relevant cluster when outlying points exist. Here the empirical covariance estimation is skewed by points outside of the main cluster. Of course, some screening tools would have pointed out the presence of two clusters (Support Vector Machines, Gaussian Mixture Models, univariate outlier detection, ...). But had it been a high-dimensional example, none of these could be applied that easily. .. GENERATED FROM PYTHON SOURCE LINES 40-52 .. code-block:: Python from sklearn.covariance import EllipticEnvelope from sklearn.inspection import DecisionBoundaryDisplay from sklearn.svm import OneClassSVM estimators = { "Empirical Covariance": EllipticEnvelope(support_fraction=1.0, contamination=0.25), "Robust Covariance (Minimum Covariance Determinant)": EllipticEnvelope( contamination=0.25 ), "OCSVM": OneClassSVM(nu=0.25, gamma=0.35), } .. GENERATED FROM PYTHON SOURCE LINES 53-97 .. code-block:: Python import matplotlib.lines as mlines import matplotlib.pyplot as plt from sklearn.datasets import load_wine X = load_wine()["data"][:, [1, 2]] # two clusters fig, ax = plt.subplots() colors = ["tab:blue", "tab:orange", "tab:red"] # Learn a frontier for outlier detection with several classifiers legend_lines = [] for color, (name, estimator) in zip(colors, estimators.items()): estimator.fit(X) DecisionBoundaryDisplay.from_estimator( estimator, X, response_method="decision_function", plot_method="contour", levels=[0], colors=color, ax=ax, ) legend_lines.append(mlines.Line2D([], [], color=color, label=name)) ax.scatter(X[:, 0], X[:, 1], color="black") bbox_args = dict(boxstyle="round", fc="0.8") arrow_args = dict(arrowstyle="->") ax.annotate( "outlying points", xy=(4, 2), xycoords="data", textcoords="data", xytext=(3, 1.25), bbox=bbox_args, arrowprops=arrow_args, ) ax.legend(handles=legend_lines, loc="upper center") _ = ax.set( xlabel="ash", ylabel="malic_acid", title="Outlier detection on a real data set (wine recognition)", ) .. image-sg:: /auto_examples/applications/images/sphx_glr_plot_outlier_detection_wine_001.png :alt: Outlier detection on a real data set (wine recognition) :srcset: /auto_examples/applications/images/sphx_glr_plot_outlier_detection_wine_001.png :class: sphx-glr-single-img .. GENERATED FROM PYTHON SOURCE LINES 98-109 Second example -------------- The second example shows the ability of the Minimum Covariance Determinant robust estimator of covariance to concentrate on the main mode of the data distribution: the location seems to be well estimated, although the covariance is hard to estimate due to the banana-shaped distribution. Anyway, we can get rid of some outlying observations. The One-Class SVM is able to capture the real data structure, but the difficulty is to adjust its kernel bandwidth parameter so as to obtain a good compromise between the shape of the data scatter matrix and the risk of over-fitting the data. .. GENERATED FROM PYTHON SOURCE LINES 109-138 .. code-block:: Python X = load_wine()["data"][:, [6, 9]] # "banana"-shaped fig, ax = plt.subplots() colors = ["tab:blue", "tab:orange", "tab:red"] # Learn a frontier for outlier detection with several classifiers legend_lines = [] for color, (name, estimator) in zip(colors, estimators.items()): estimator.fit(X) DecisionBoundaryDisplay.from_estimator( estimator, X, response_method="decision_function", plot_method="contour", levels=[0], colors=color, ax=ax, ) legend_lines.append(mlines.Line2D([], [], color=color, label=name)) ax.scatter(X[:, 0], X[:, 1], color="black") ax.legend(handles=legend_lines, loc="upper center") ax.set( xlabel="flavanoids", ylabel="color_intensity", title="Outlier detection on a real data set (wine recognition)", ) plt.show() .. image-sg:: /auto_examples/applications/images/sphx_glr_plot_outlier_detection_wine_002.png :alt: Outlier detection on a real data set (wine recognition) :srcset: /auto_examples/applications/images/sphx_glr_plot_outlier_detection_wine_002.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 0.340 seconds) .. _sphx_glr_download_auto_examples_applications_plot_outlier_detection_wine.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: binder-badge .. image:: images/binder_badge_logo.svg :target: https://mybinder.org/v2/gh/scikit-learn/scikit-learn/main?urlpath=lab/tree/notebooks/auto_examples/applications/plot_outlier_detection_wine.ipynb :alt: Launch binder :width: 150 px .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: plot_outlier_detection_wine.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: plot_outlier_detection_wine.py ` .. container:: sphx-glr-download sphx-glr-download-zip :download:`Download zipped: plot_outlier_detection_wine.zip ` .. include:: plot_outlier_detection_wine.recommendations .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_