I\'m doing different text classification experiments. Now I need to calculate the AUC-ROC for each task. For the binary classifications, I already made it work with this cod
As people mentioned in comments you have to convert your problem into binary by using OneVsAll
approach, so you'll have n_class
number of ROC curves.
A simple example:
from sklearn.metrics import roc_curve, auc
from sklearn import datasets
from sklearn.multiclass import OneVsRestClassifier
from sklearn.svm import LinearSVC
from sklearn.preprocessing import label_binarize
from sklearn.cross_validation import train_test_split
import matplotlib.pyplot as plt
iris = datasets.load_iris()
X, y = iris.data, iris.target
y = label_binarize(y, classes=[0,1,2])
n_classes = 3
# shuffle and split training and test sets
X_train, X_test, y_train, y_test =\
train_test_split(X, y, test_size=0.33, random_state=0)
# classifier
clf = OneVsRestClassifier(LinearSVC(random_state=0))
y_score = clf.fit(X_train, y_train).decision_function(X_test)
# Compute ROC curve and ROC area for each class
fpr = dict()
tpr = dict()
roc_auc = dict()
for i in range(n_classes):
fpr[i], tpr[i], _ = roc_curve(y_test[:, i], y_score[:, i])
roc_auc[i] = auc(fpr[i], tpr[i])
# Plot of a ROC curve for a specific class
for i in range(n_classes):
plt.figure()
plt.plot(fpr[i], tpr[i], label='ROC curve (area = %0.2f)' % roc_auc[i])
plt.plot([0, 1], [0, 1], 'k--')
plt.xlim([0.0, 1.0])
plt.ylim([0.0, 1.05])
plt.xlabel('False Positive Rate')
plt.ylabel('True Positive Rate')
plt.title('Receiver operating characteristic example')
plt.legend(loc="lower right")
plt.show()