File Content: plot_compare_reduction.py #!/usr/bin/python # -*- coding: utf-8 -*- """ ================================================================= Selecting dimensionality reduction with Pipeline and GridSearchCV ================================================================= This example constructs a pipeline that does dimensionality reduction followed by prediction with a support vector classifier. It demonstrates the use of GridSearchCV and Pipeline to optimize over different classes of estimators in a single CV run -- unsupervised PCA and NMF dimensionality reductions are compared to univariate feature selection during the grid search. """ # Authors: Robert McGibbon, Joel Nothman from __future__ import print_function, division import numpy as np import matplotlib.pyplot as plt from sklearn.datasets import load_digits from sklearn.model_selection import GridSearchCV from sklearn.pipeline import Pipeline from sklearn.svm import LinearSVC from sklearn.decomposition import PCA, NMF from sklearn.feature_selection import SelectKBest, chi2 print(__doc__) pipe = Pipeline([ ('reduce_dim', PCA()), ('classify', LinearSVC()) ]) N_FEATURES_OPTIONS = [2, 4, 8] C_OPTIONS = [1, 10, 100, 1000] param_grid = [ { 'reduce_dim': [PCA(iterated_power=7), NMF()], 'reduce_dim__n_components': N_FEATURES_OPTIONS, 'classify__C': C_OPTIONS }, { 'reduce_dim': [SelectKBest(chi2)], 'reduce_dim__k': N_FEATURES_OPTIONS, 'classify__C': C_OPTIONS }, ] reducer_labels = ['PCA', 'NMF', 'KBest(chi2)'] grid = GridSearchCV(pipe, cv=3, n_jobs=2, param_grid=param_grid) digits = load_digits() grid.fit(digits.data, digits.target) mean_scores = np.array(grid.cv_results_['mean_test_score']) # scores are in the order of param_grid iteration, which is alphabetical mean_scores = mean_scores.reshape(len(C_OPTIONS), -1, len(N_FEATURES_OPTIONS)) # select score for best C mean_scores = mean_scores.max(axis=0) bar_offsets = (np.arange(len(N_FEATURES_OPTIONS)) * (len(reducer_labels) + 1) + .5) plt.figure() COLORS = 'bgrcmyk' for i, (label, reducer_scores) in enumerate(zip(reducer_labels, mean_scores)): plt.bar(bar_offsets + i, reducer_scores, label=label, color=COLORS[i]) plt.title("Comparing feature reduction techniques") plt.xlabel('Reduced number of features') plt.xticks(bar_offsets + len(reducer_labels) / 2, N_FEATURES_OPTIONS) plt.ylabel('Digit classification accuracy') plt.ylim((0, 1)) plt.legend(loc='upper left') plt.show() Submit