ENH add label ranking average precision
DOC write narrative doc for label ranking average precision
DOC FIX error + wording
TST invariance testing + handle degenerate case
flake8
FIX use np.bincount
DOC friendlier narrative documentation
ENH simplify label ranking average precision (thanks @jnothman)
ENH be backward compatible for old version of scipy
Typo
pep8
DOC remove confusing mention to mean average precision
DOC improve documentatino thanks to @vene and remove mention of relevant labels
DOC more intuition about corner case
DOC add documentation to backported function
ENH less nested code
FIX encoding issue
Merge pull request #2804 from arjoly/lrap

[MRG+1] Label ranking average precision