.. _sphx_glr_auto_examples_ensemble_plot_feature_transformation.py: =============================================== Feature transformations with ensembles of trees =============================================== Transform your features into a higher dimensional, sparse space. Then train a linear model on these features. First fit an ensemble of trees (totally random trees, a random forest, or gradient boosted trees) on the training set. Then each leaf of each tree in the ensemble is assigned a fixed arbitrary feature index in a new feature space. These leaf indices are then encoded in a one-hot fashion. Each sample goes through the decisions of each tree of the ensemble and ends up in one leaf per tree. The sample is encoded by setting feature values for these leaves to 1 and the other feature values to 0. The resulting transformer has then learned a supervised, sparse, high-dimensional categorical embedding of the data. .. rst-class:: sphx-glr-horizontal * .. image:: /auto_examples/ensemble/images/sphx_glr_plot_feature_transformation_001.png :scale: 47 * .. image:: /auto_examples/ensemble/images/sphx_glr_plot_feature_transformation_002.png :scale: 47 .. code-block:: python # Author: Tim Head # # License: BSD 3 clause import numpy as np np.random.seed(10) import matplotlib.pyplot as plt from sklearn.datasets import make_classification from sklearn.linear_model import LogisticRegression from sklearn.ensemble import (RandomTreesEmbedding, RandomForestClassifier, GradientBoostingClassifier) from sklearn.preprocessing import OneHotEncoder from sklearn.model_selection import train_test_split from sklearn.metrics import roc_curve from sklearn.pipeline import make_pipeline n_estimator = 10 X, y = make_classification(n_samples=80000) X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.5) # It is important to train the ensemble of trees on a different subset # of the training data than the linear regression model to avoid # overfitting, in particular if the total number of leaves is # similar to the number of training samples X_train, X_train_lr, y_train, y_train_lr = train_test_split(X_train, y_train, test_size=0.5) # Unsupervised transformation based on totally random trees rt = RandomTreesEmbedding(max_depth=3, n_estimators=n_estimator, random_state=0) rt_lm = LogisticRegression() pipeline = make_pipeline(rt, rt_lm) pipeline.fit(X_train, y_train) y_pred_rt = pipeline.predict_proba(X_test)[:, 1] fpr_rt_lm, tpr_rt_lm, _ = roc_curve(y_test, y_pred_rt) # Supervised transformation based on random forests rf = RandomForestClassifier(max_depth=3, n_estimators=n_estimator) rf_enc = OneHotEncoder() rf_lm = LogisticRegression() rf.fit(X_train, y_train) rf_enc.fit(rf.apply(X_train)) rf_lm.fit(rf_enc.transform(rf.apply(X_train_lr)), y_train_lr) y_pred_rf_lm = rf_lm.predict_proba(rf_enc.transform(rf.apply(X_test)))[:, 1] fpr_rf_lm, tpr_rf_lm, _ = roc_curve(y_test, y_pred_rf_lm) grd = GradientBoostingClassifier(n_estimators=n_estimator) grd_enc = OneHotEncoder() grd_lm = LogisticRegression() grd.fit(X_train, y_train) grd_enc.fit(grd.apply(X_train)[:, :, 0]) grd_lm.fit(grd_enc.transform(grd.apply(X_train_lr)[:, :, 0]), y_train_lr) y_pred_grd_lm = grd_lm.predict_proba( grd_enc.transform(grd.apply(X_test)[:, :, 0]))[:, 1] fpr_grd_lm, tpr_grd_lm, _ = roc_curve(y_test, y_pred_grd_lm) # The gradient boosted model by itself y_pred_grd = grd.predict_proba(X_test)[:, 1] fpr_grd, tpr_grd, _ = roc_curve(y_test, y_pred_grd) # The random forest model by itself y_pred_rf = rf.predict_proba(X_test)[:, 1] fpr_rf, tpr_rf, _ = roc_curve(y_test, y_pred_rf) plt.figure(1) plt.plot([0, 1], [0, 1], 'k--') plt.plot(fpr_rt_lm, tpr_rt_lm, label='RT + LR') plt.plot(fpr_rf, tpr_rf, label='RF') plt.plot(fpr_rf_lm, tpr_rf_lm, label='RF + LR') plt.plot(fpr_grd, tpr_grd, label='GBT') plt.plot(fpr_grd_lm, tpr_grd_lm, label='GBT + LR') plt.xlabel('False positive rate') plt.ylabel('True positive rate') plt.title('ROC curve') plt.legend(loc='best') plt.show() plt.figure(2) plt.xlim(0, 0.2) plt.ylim(0.8, 1) plt.plot([0, 1], [0, 1], 'k--') plt.plot(fpr_rt_lm, tpr_rt_lm, label='RT + LR') plt.plot(fpr_rf, tpr_rf, label='RF') plt.plot(fpr_rf_lm, tpr_rf_lm, label='RF + LR') plt.plot(fpr_grd, tpr_grd, label='GBT') plt.plot(fpr_grd_lm, tpr_grd_lm, label='GBT + LR') plt.xlabel('False positive rate') plt.ylabel('True positive rate') plt.title('ROC curve (zoomed in at top left)') plt.legend(loc='best') plt.show() **Total running time of the script:** (0 minutes 2.023 seconds) .. container:: sphx-glr-download **Download Python source code:** :download:`plot_feature_transformation.py ` .. container:: sphx-glr-download **Download IPython notebook:** :download:`plot_feature_transformation.ipynb `