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.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "auto_examples/svm/plot_svm_anova.py"
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.. only:: html

    .. note::
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        Click :ref:`here <sphx_glr_download_auto_examples_svm_plot_svm_anova.py>`
        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_svm_plot_svm_anova.py:


=================================================
SVM-Anova: SVM with univariate feature selection
=================================================

This example shows how to perform univariate feature selection before running a
SVC (support vector classifier) to improve the classification scores. We use
the iris dataset (4 features) and add 36 non-informative features. We can find
that our model achieves best performance when we select around 10% of features.

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Load some data to play with
---------------------------

.. GENERATED FROM PYTHON SOURCE LINES 16-25

.. code-block:: default

    import numpy as np
    from sklearn.datasets import load_iris

    X, y = load_iris(return_X_y=True)

    # Add non-informative features
    rng = np.random.RandomState(0)
    X = np.hstack((X, 2 * rng.random((X.shape[0], 36))))








.. GENERATED FROM PYTHON SOURCE LINES 26-28

Create the pipeline
-------------------

.. GENERATED FROM PYTHON SOURCE LINES 28-44

.. code-block:: default

    from sklearn.pipeline import Pipeline
    from sklearn.feature_selection import SelectPercentile, chi2
    from sklearn.preprocessing import StandardScaler
    from sklearn.svm import SVC

    # Create a feature-selection transform, a scaler and an instance of SVM that we
    # combine together to have a full-blown estimator

    clf = Pipeline(
        [
            ("anova", SelectPercentile(chi2)),
            ("scaler", StandardScaler()),
            ("svc", SVC(gamma="auto")),
        ]
    )








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Plot the cross-validation score as a function of percentile of features
-----------------------------------------------------------------------

.. GENERATED FROM PYTHON SOURCE LINES 47-67

.. code-block:: default

    import matplotlib.pyplot as plt
    from sklearn.model_selection import cross_val_score

    score_means = list()
    score_stds = list()
    percentiles = (1, 3, 6, 10, 15, 20, 30, 40, 60, 80, 100)

    for percentile in percentiles:
        clf.set_params(anova__percentile=percentile)
        this_scores = cross_val_score(clf, X, y)
        score_means.append(this_scores.mean())
        score_stds.append(this_scores.std())

    plt.errorbar(percentiles, score_means, np.array(score_stds))
    plt.title("Performance of the SVM-Anova varying the percentile of features selected")
    plt.xticks(np.linspace(0, 100, 11, endpoint=True))
    plt.xlabel("Percentile")
    plt.ylabel("Accuracy Score")
    plt.axis("tight")
    plt.show()



.. image-sg:: /auto_examples/svm/images/sphx_glr_plot_svm_anova_001.png
   :alt: Performance of the SVM-Anova varying the percentile of features selected
   :srcset: /auto_examples/svm/images/sphx_glr_plot_svm_anova_001.png
   :class: sphx-glr-single-img






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   **Total running time of the script:** ( 0 minutes  0.257 seconds)


.. _sphx_glr_download_auto_examples_svm_plot_svm_anova.py:

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