Cross-validation on Digits Dataset Exercise

A tutorial exercise using Cross-validation with an SVM on the Digits dataset.

This exercise is used in the Cross-validation generators part of the Model selection: choosing estimators and their parameters section of the A tutorial on statistical-learning for scientific data processing.

../../_images/sphx_glr_plot_cv_digits_001.png

print(__doc__)
 
 
import numpy as np
from sklearn.model_selection import cross_val_score
from sklearn import datasets, svm
 
digits = datasets.load_digits()
X = digits.data
y = digits.target
 
svc = svm.SVC(kernel='linear')
C_s = np.logspace(-10, 0, 10)
 
scores = list()
scores_std = list()
for C in C_s:
    svc.C = C
    this_scores = cross_val_score(svc, X, y, n_jobs=1)
    scores.append(np.mean(this_scores))
    scores_std.append(np.std(this_scores))
 
# Do the plotting
import matplotlib.pyplot as plt
plt.figure(1, figsize=(4, 3))
plt.clf()
plt.semilogx(C_s, scores)
plt.semilogx(C_s, np.array(scores) + np.array(scores_std), 'b--')
plt.semilogx(C_s, np.array(scores) - np.array(scores_std), 'b--')
locs, labels = plt.yticks()
plt.yticks(locs, list(map(lambda x: "%g" % x, locs)))
plt.ylabel('CV score')
plt.xlabel('Parameter C')
plt.ylim(0, 1.1)
plt.show()

Total running time of the script: (0 minutes 5.397 seconds)

Download Python source code: plot_cv_digits.py

Download IPython notebook: plot_cv_digits.ipynb

Links:

http://scikit-learn.org/stable/auto_examples/exercises/plot_cv_digits.html

doc_scikit_learn

2025-01-10 15:47:30

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