BUG: don't exclude non-numeric data in groupby.max/min. close #2700

Author: wesm

RELEASE.rst

@@ -88,6 +88,7 @@ pandas 0.10.1
   - Fix DataFrame.from_records corner case when passed columns, index column,
     but empty record list (GH2633_)
   - Fix C parser-tokenizer bug with trailing fields. (GH2668_)
+  - Don't exclude non-numeric data from GroupBy.max/min (GH2700_)
 
 **API Changes**
 
@@ -114,6 +115,7 @@ pandas 0.10.1
 .. _GH2690: https://github.com/pydata/pandas/issues/2690
 .. _GH2692: https://github.com/pydata/pandas/issues/2692
 .. _GH2699: https://github.com/pydata/pandas/issues/2699
+.. _GH2700: https://github.com/pydata/pandas/issues/2700
 
 pandas 0.10.0
 =============

pandas/core/groupby.py

@@ -401,8 +401,8 @@ def size(self):
 
     sum = _groupby_function('sum', 'add', np.sum)
     prod = _groupby_function('prod', 'prod', np.prod)
-    min = _groupby_function('min', 'min', np.min)
-    max = _groupby_function('max', 'max', np.max)
+    min = _groupby_function('min', 'min', np.min, numeric_only=False)
+    max = _groupby_function('max', 'max', np.max, numeric_only=False)
     first = _groupby_function('first', 'first', _first_compat,
                               numeric_only=False, _convert=True)
     last = _groupby_function('last', 'last', _last_compat, numeric_only=False,

pandas/tests/test_groupby.py

@@ -1083,6 +1083,16 @@ def _testit(op):
         _testit(lambda x: x.min())
         _testit(lambda x: x.max())
 
+    def test_max_min_non_numeric(self):
+        # #2700
+        aa = DataFrame({'nn':[11,11,22,22],'ii':[1,2,3,4],'ss':4*['mama']})
+
+        result = aa.groupby('nn').max()
+        self.assertTrue('ss' in result)
+
+        result = aa.groupby('nn').min()
+        self.assertTrue('ss' in result)
+
     def test_cython_agg_boolean(self):
         frame = DataFrame({'a': np.random.randint(0, 5, 50),
                            'b': np.random.randint(0, 2, 50).astype('bool')})