scikit-learn/scikit-learn — pull request #3744 by MechCoder (2014-10-08 16:28:13+00:00)
Title: FIX: Raise warnings in f_classif a given feature is constant across each class

Fixes https://github.com/scikit-learn/scikit-learn/issues/2359

This is because for each class, the variation within the samples is zero, which technically gives a F score of inf.