Updated whatsnew

WillAyd · WillAyd · commit 8d658c5516ff · 2018-02-07T12:31:56.000-08:00
diff --git a/doc/source/whatsnew/v0.23.0.txt b/doc/source/whatsnew/v0.23.0.txt
@@ -579,6 +579,7 @@ Performance Improvements
 - Improved performance of :func:`DataFrame.median` with ``axis=1`` when bottleneck is not installed (:issue:`16468`)
 - Improved performance of :func:`MultiIndex.get_loc` for large indexes, at the cost of a reduction in performance for small ones (:issue:`18519`)
 - Improved performance of pairwise ``.rolling()`` and ``.expanding()`` with ``.cov()`` and ``.corr()`` operations (:issue:`17917`)
+- Improved performance of :func:`DataFrameGroupBy.rank` (:issue:`15779`)
 
 .. _whatsnew_0230.docs:
 
