What does recall mean in Machine Learning?

Question

I know that the meaning of recall in search engine, but what\'s the meaning of recall of a classifier, e.g. bayes classifier? please give a an example, thanks.

for examp

Answer 1

Precision in ML is the same as in Information Retrieval.

recall = TP / (TP + FN)
precision = TP / (TP + FP)

(Where TP = True Positive, TN = True Negative, FP = False Positive, FN = False Negative).

It makes sense to use these notations for binary classifier, usually the "positive" is the less common classification. Note that the precision/recall metrics is actually the specific form where #classes=2 for the more general confusion matrix.

Also, your notation of "precision" is actually accuracy, and is (TP+TN)/ ALL