Mastering Machine Learning with scikit-learn - Second Edition

Precision and recall

Recall that precision is the fraction of positive predictions that are correct. In our SMS spam classifier, precision is the fraction of messages classified as spam that are actually spam. Sometimes called sensitivity in medical domains, recall is the fraction of the truly positive instances that the classifier recognized. A recall score of 1 indicates that the classifier did not make any false negative predictions. For our SMS spam classifier, recall is the fraction of truly spam messages that were classified as spam.

Individually, precision and recall are seldom informative; they are both incomplete views of a classifier's performance. Both precision and recall can fail to distinguish classifiers that perform well from ...