From 7b34fbacee68fe059d5309aed3484c2ed1c7e37f Mon Sep 17 00:00:00 2001
From: Gael Varoquaux <gael.varoquaux@normalesup.org>
Date: Mon, 7 May 2012 08:22:44 +0200
Subject: [PATCH] DOC: Feature extraction vs feature selection

---
 doc/modules/feature_extraction.rst | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/doc/modules/feature_extraction.rst b/doc/modules/feature_extraction.rst
index 5e3c0985ba..33447dfdc0 100644
--- a/doc/modules/feature_extraction.rst
+++ b/doc/modules/feature_extraction.rst
@@ -11,6 +11,13 @@ The :mod:`sklearn.feature_extraction` module can be used to extract
 features in a format supported by machine learning algorithms from datasets
 consisting of formats such as text and image.
 
+.. note::
+
+   Feature extraction is very different from :ref:`feature_selection`:
+   the former consists in transforming arbitrary data, such as text or
+   images, into numerical features usable for machine learning. The later
+   is a machine learning technique applied on these features.
+
 .. _dict_feature_extraction:
 
 Loading features from dicts
-- 
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