scikit-learn/scikit-learn — comment on commit 872e70d9b715be074aa761cbd9c40e29afd64d4f
File:  line 0
By amueller:

@ your second comment:
If X=0, factor=0 as far as I can see, so there should be no problem. I'm not sure what happens when one takes log() of a sparse matrix, though.

Maybe one should do all the operations only where X!=0. Would that slow down things in the dense case?