[MRG] DOC add pre-processing section in related projects
@@ -184,6 +184,16 @@ and tasks.
K-means and mixture of von Mises Fisher clustering routines for data on the
unit hypersphere.
+**Pre-processing**
+
+- `categorical-encoding
+ <https://github.com/scikit-learn-contrib/categorical-encoding>`_ A
+ library of sklearn compatible categorical variable encoders.
+
+- `imbalanced-learn
+ <https://github.com/scikit-learn-contrib/imbalanced-learn>`_ Various
+ methods to under- and over-sample datasets.
+
Statistical learning with Python
--------------------------------
Other packages useful for data analysis and machine learning.
