Jointly tuning gamma and C with GridSearchCV

In the previous exercise the best value of gamma was 0.001 using the default value of C, which is 1. In this exercise you'll search for the best combination of C and gamma using GridSearchCV.

As in the previous exercise, the 2-vs-not-2 digits dataset is already loaded, but this time it's split into the variables X_train, y_train, X_test, and y_test. Even though cross-validation already splits the training set into parts, it's often a good idea to hold out a separate test set to make sure the cross-validation results are sensible.

Deze oefening maakt deel uit van de cursus

Linear Classifiers in Python

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Oefeninstructies

Run GridSearchCV to find the best hyperparameters using the training set.
Print the best values of the parameters.
Print out the accuracy on the test set, which was not used during the cross-validation procedure.

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

# Instantiate an RBF SVM
svm = SVC()

# Instantiate the GridSearchCV object and run the search
parameters = {'C':[0.1, 1, 10], 'gamma':[0.00001, 0.0001, 0.001, 0.01, 0.1]}
searcher = GridSearchCV(svm, ____)
____.fit(____)

# Report the best parameters and the corresponding score
print("Best CV params", searcher.best_params_)
print("Best CV accuracy", searcher.best_score_)

# Report the test accuracy using these best parameters
print("Test accuracy of best grid search hypers:", searcher.score(____))

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