.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "auto_examples/linear_model/plot_sparse_logistic_regression_20newsgroups.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 JupyterLite or Binder .. rst-class:: sphx-glr-example-title .. _sphx_glr_auto_examples_linear_model_plot_sparse_logistic_regression_20newsgroups.py: ==================================================== Multiclass sparse logistic regression on 20newgroups ==================================================== Comparison of multinomial logistic L1 vs one-versus-rest L1 logistic regression to classify documents from the newgroups20 dataset. Multinomial logistic regression yields more accurate results and is faster to train on the larger scale dataset. Here we use the l1 sparsity that trims the weights of not informative features to zero. This is good if the goal is to extract the strongly discriminative vocabulary of each class. If the goal is to get the best predictive accuracy, it is better to use the non sparsity-inducing l2 penalty instead. A more traditional (and possibly better) way to predict on a sparse subset of input features would be to use univariate feature selection followed by a traditional (l2-penalised) logistic regression model. .. GENERATED FROM PYTHON SOURCE LINES 22-126 .. image-sg:: /auto_examples/linear_model/images/sphx_glr_plot_sparse_logistic_regression_20newsgroups_001.png :alt: Multinomial vs One-vs-Rest Logistic L1 Dataset 20newsgroups :srcset: /auto_examples/linear_model/images/sphx_glr_plot_sparse_logistic_regression_20newsgroups_001.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-script-out .. code-block:: none Dataset 20newsgroup, train_samples=4500, n_features=130107, n_classes=20 [model=One versus Rest, solver=saga] Number of epochs: 1 [model=One versus Rest, solver=saga] Number of epochs: 2 [model=One versus Rest, solver=saga] Number of epochs: 3 Test accuracy for model ovr: 0.5960 % non-zero coefficients for model ovr, per class: [0.26593496 0.43348936 0.26362917 0.31973683 0.37815029 0.2928359 0.27054655 0.62717609 0.19522393 0.30897646 0.34586917 0.28207552 0.34125758 0.29898468 0.34279478 0.59489497 0.38353048 0.35278655 0.19829832 0.14603365] Run time (3 epochs) for model ovr:1.20 [model=Multinomial, solver=saga] Number of epochs: 1 [model=Multinomial, solver=saga] Number of epochs: 2 [model=Multinomial, solver=saga] Number of epochs: 5 Test accuracy for model multinomial: 0.6440 % non-zero coefficients for model multinomial, per class: [0.36047253 0.1268187 0.10606655 0.17985197 0.5395559 0.07993421 0.06686804 0.21443888 0.11528972 0.2075215 0.10914094 0.11144673 0.13988486 0.09684337 0.26286057 0.11682692 0.55800226 0.17370318 0.11452112 0.14603365] Run time (5 epochs) for model multinomial:1.04 Example run in 5.060 s | .. code-block:: Python # Author: Arthur Mensch import timeit import warnings import matplotlib.pyplot as plt import numpy as np from sklearn.datasets import fetch_20newsgroups_vectorized from sklearn.exceptions import ConvergenceWarning from sklearn.linear_model import LogisticRegression from sklearn.model_selection import train_test_split warnings.filterwarnings("ignore", category=ConvergenceWarning, module="sklearn") t0 = timeit.default_timer() # We use SAGA solver solver = "saga" # Turn down for faster run time n_samples = 5000 X, y = fetch_20newsgroups_vectorized(subset="all", return_X_y=True) X = X[:n_samples] y = y[:n_samples] X_train, X_test, y_train, y_test = train_test_split( X, y, random_state=42, stratify=y, test_size=0.1 ) train_samples, n_features = X_train.shape n_classes = np.unique(y).shape[0] print( "Dataset 20newsgroup, train_samples=%i, n_features=%i, n_classes=%i" % (train_samples, n_features, n_classes) ) models = { "ovr": {"name": "One versus Rest", "iters": [1, 2, 3]}, "multinomial": {"name": "Multinomial", "iters": [1, 2, 5]}, } for model in models: # Add initial chance-level values for plotting purpose accuracies = [1 / n_classes] times = [0] densities = [1] model_params = models[model] # Small number of epochs for fast runtime for this_max_iter in model_params["iters"]: print( "[model=%s, solver=%s] Number of epochs: %s" % (model_params["name"], solver, this_max_iter) ) lr = LogisticRegression( solver=solver, multi_class=model, penalty="l1", max_iter=this_max_iter, random_state=42, ) t1 = timeit.default_timer() lr.fit(X_train, y_train) train_time = timeit.default_timer() - t1 y_pred = lr.predict(X_test) accuracy = np.sum(y_pred == y_test) / y_test.shape[0] density = np.mean(lr.coef_ != 0, axis=1) * 100 accuracies.append(accuracy) densities.append(density) times.append(train_time) models[model]["times"] = times models[model]["densities"] = densities models[model]["accuracies"] = accuracies print("Test accuracy for model %s: %.4f" % (model, accuracies[-1])) print( "%% non-zero coefficients for model %s, per class:\n %s" % (model, densities[-1]) ) print( "Run time (%i epochs) for model %s:%.2f" % (model_params["iters"][-1], model, times[-1]) ) fig = plt.figure() ax = fig.add_subplot(111) for model in models: name = models[model]["name"] times = models[model]["times"] accuracies = models[model]["accuracies"] ax.plot(times, accuracies, marker="o", label="Model: %s" % name) ax.set_xlabel("Train time (s)") ax.set_ylabel("Test accuracy") ax.legend() fig.suptitle("Multinomial vs One-vs-Rest Logistic L1\nDataset %s" % "20newsgroups") fig.tight_layout() fig.subplots_adjust(top=0.85) run_time = timeit.default_timer() - t0 print("Example run in %.3f s" % run_time) plt.show() .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 5.125 seconds) .. _sphx_glr_download_auto_examples_linear_model_plot_sparse_logistic_regression_20newsgroups.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/linear_model/plot_sparse_logistic_regression_20newsgroups.ipynb :alt: Launch binder :width: 150 px .. container:: lite-badge .. image:: images/jupyterlite_badge_logo.svg :target: ../../lite/lab/?path=auto_examples/linear_model/plot_sparse_logistic_regression_20newsgroups.ipynb :alt: Launch JupyterLite :width: 150 px .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: plot_sparse_logistic_regression_20newsgroups.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: plot_sparse_logistic_regression_20newsgroups.py ` .. include:: plot_sparse_logistic_regression_20newsgroups.recommendations .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_