From 5c839238c33bc8cc5030e9a84efc23f194a47853 Mon Sep 17 00:00:00 2001
From: Caleb Epstein <cae@bklyn.org>
Date: Wed, 22 Jan 2014 12:28:45 -0500
Subject: [PATCH] Add -NaN and -nan to default NA values

---
 doc/source/io.rst               | 2 +-
 doc/source/release.rst          | 2 ++
 doc/source/v0.13.1.txt          | 3 +++
 pandas/io/parsers.py            | 2 +-
 pandas/io/tests/test_parsers.py | 5 +++--
 5 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/doc/source/io.rst b/doc/source/io.rst
index cba81a8b39600..fdad28688b7c6 100644
--- a/doc/source/io.rst
+++ b/doc/source/io.rst
@@ -575,7 +575,7 @@ the corresponding equivalent values will also imply a missing value (in this cas
 
 To completely override the default values that are recognized as missing, specify ``keep_default_na=False``.
 The default ``NaN`` recognized values are ``['-1.#IND', '1.#QNAN', '1.#IND', '-1.#QNAN', '#N/A','N/A', 'NA',
-'#NA', 'NULL', 'NaN', 'nan']``.
+'#NA', 'NULL', 'NaN', '-NaN', 'nan', '-nan']``.
 
 .. code-block:: python
 
diff --git a/doc/source/release.rst b/doc/source/release.rst
index 3cee4473aab66..e1325c676340e 100644
--- a/doc/source/release.rst
+++ b/doc/source/release.rst
@@ -64,6 +64,8 @@ API Changes
   - ``autocorrelation_plot`` now accepts ``**kwargs``. (:issue:`5623`)
   - ``convert_objects`` now accepts a ``convert_timedeltas='coerce'`` argument to allow forced dtype conversion of
     timedeltas (:issue:`5458`,:issue:`5689`)
+  - Add ``-NaN`` and ``-nan`` to the default set of NA values
+    (:issue:`5952`).  See :ref:`NA Values <io.na_values>`.
 
 Experimental Features
 ~~~~~~~~~~~~~~~~~~~~~
diff --git a/doc/source/v0.13.1.txt b/doc/source/v0.13.1.txt
index 08c8eb76caaf8..33dc92343427b 100644
--- a/doc/source/v0.13.1.txt
+++ b/doc/source/v0.13.1.txt
@@ -18,6 +18,9 @@ There are several new or updated docs sections including:
 API changes
 ~~~~~~~~~~~
 
+- Add ``-NaN`` and ``-nan`` to the default set of NA values (:issue:`5952`).
+  See :ref:`NA Values <io.na_values>`.
+
 Prior Version Deprecations/Changes
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/pandas/io/parsers.py b/pandas/io/parsers.py
index 796475aa24a58..689d4aab48758 100644
--- a/pandas/io/parsers.py
+++ b/pandas/io/parsers.py
@@ -449,7 +449,7 @@ def read_fwf(filepath_or_buffer, colspecs='infer', widths=None, **kwds):
 # '1.#INF','-1.#INF', '1.#INF000000',
 _NA_VALUES = set([
     '-1.#IND', '1.#QNAN', '1.#IND', '-1.#QNAN', '#N/A', 'N/A', 'NA', '#NA',
-    'NULL', 'NaN', 'nan', ''
+    'NULL', 'NaN', '-NaN', 'nan', '-nan', ''
 ])
 
 
diff --git a/pandas/io/tests/test_parsers.py b/pandas/io/tests/test_parsers.py
index f04c055692386..76006507be524 100644
--- a/pandas/io/tests/test_parsers.py
+++ b/pandas/io/tests/test_parsers.py
@@ -33,6 +33,7 @@
 import pandas.tseries.tools as tools
 
 from numpy.testing.decorators import slow
+from numpy.testing import assert_array_equal
 
 from pandas.parser import OverflowError
 
@@ -685,8 +686,8 @@ def test_non_string_na_values(self):
     def test_default_na_values(self):
         _NA_VALUES = set(['-1.#IND', '1.#QNAN', '1.#IND', '-1.#QNAN',
                           '#N/A','N/A', 'NA', '#NA', 'NULL', 'NaN',
-                          'nan', ''])
-
+                          'nan', '-NaN', '-nan', ''])
+        assert_array_equal (_NA_VALUES, parsers._NA_VALUES)
         nv = len(_NA_VALUES)
         def f(i, v):
             if i == 0: