BUG: DataFrame.align bug with join keyword (GH13914)

doc/source/whatsnew/v0.18.2.txt

@@ -149,3 +149,4 @@ Bug Fixes
 - Bug in ``NaT`` - ``Period`` raises ``AttributeError`` (:issue:`13071`)
 - Bug in ``Period`` addition raises ``TypeError`` if ``Period`` is on right hand side (:issue:`13069`)
 - Bug in ``pd.set_eng_float_format()`` that would prevent NaN's from formatting (:issue:`11981`)
+- Fixed the bug in ``DataFrame.align()`` which was giving wrong output when supplied with the ``join`` argument. Earlier, upon supplying value of join argument as any of the four('outer', 'inner', 'left', 'right' ), align() was giving erraneous output. Align with broadcast_axis specified was using 'inner' join consistently irrespective of the value of 'join' provided when aligning dataframe and series on other axis. The problem was identified to be in pandas/core/generic.py and has been subsequently fixed. (:issue:`13194`) 

pandas/core/generic.py

@@ -4147,13 +4147,17 @@ def align(self, other, join='outer', axis=None, level=None, copy=True,
         from pandas import DataFrame, Series
         method = missing.clean_fill_method(method)
 
+        if axis is not None:
+            axis = self._get_axis_number(axis)
+
         if broadcast_axis == 1 and self.ndim != other.ndim:
             if isinstance(self, Series):
                 # this means other is a DataFrame, and we need to broadcast
                 # self
                 cons = self._constructor_expanddim
                 df = cons(dict((c, self) for c in other.columns),
-                          **other._construct_axes_dict())
+                          **self._construct_axes_dict(
+                          **other._construct_axes_dict(axes=['columns'])))
                 return df._align_frame(other, join=join, axis=axis,
                                        level=level, copy=copy,
                                        fill_value=fill_value, method=method,
@@ -4163,14 +4167,13 @@ def align(self, other, join='outer', axis=None, level=None, copy=True,
                 # other
                 cons = other._constructor_expanddim
                 df = cons(dict((c, other) for c in self.columns),
-                          **self._construct_axes_dict())
+                          **other._construct_axes_dict(
+                          **self._construct_axes_dict(axes=['columns'])))
                 return self._align_frame(df, join=join, axis=axis, level=level,
                                          copy=copy, fill_value=fill_value,
                                          method=method, limit=limit,
                                          fill_axis=fill_axis)
 
-        if axis is not None:
-            axis = self._get_axis_number(axis)
         if isinstance(other, DataFrame):
             return self._align_frame(other, join=join, axis=axis, level=level,
                                      copy=copy, fill_value=fill_value,

pandas/tests/frame/test_axis_select_reindex.py

@@ -880,3 +880,66 @@ def test_reindex_multi(self):
         expected = df.reindex([0, 1]).reindex(columns=['a', 'b'])
 
         assert_frame_equal(result, expected)
+
+    def test_align_broadcast_axis(self):
+        # GH 13194
+        # First four tests for DataFrame.align(Index)
+        # For 'right' join
+        df = DataFrame(np.array([[1., 2.], [3., 4.]]), columns=list('AB'))
+        ts = Series([5., 6., 7.])
+
+        result = df.align(ts, join='right', axis=0, broadcast_axis=1)
+        expected1 = DataFrame(np.array([[1., 2.], [3., 4.],
+                                        [pd.np.nan, pd.np.nan]]),
+                              columns=list('AB'))
+        expected2 = DataFrame(np.array([[5., 5.], [6., 6.], [7., 7.]]),
+                              columns=list('AB'))
+        assert_frame_equal(result[0], expected1)
+        assert_frame_equal(result[1], expected2)
+
+        # For 'right' join on different index
+        result = df.align(ts, join='right', axis=1, broadcast_axis=1)
+        expected1 = DataFrame(np.array([[1., 2.], [3., 4.]]),
+                              columns=list('AB'))
+        expected2 = DataFrame(np.array([[5., 5.], [6., 6.],
+                                        [7., 7.]]),
+                              columns=list('AB'))
+        assert_frame_equal(result[0], expected1)
+        assert_frame_equal(result[1], expected2)
+
+        # For 'left' join
+        result = df.align(ts, join='left', axis=0, broadcast_axis=1)
+        expected1 = DataFrame(np.array([[1., 2.], [3., 4.]]),
+                              columns=list('AB'))
+        expected2 = DataFrame(np.array([[5., 5.], [6., 6.]]),
+                              columns=list('AB'))
+        assert_frame_equal(result[0], expected1)
+        assert_frame_equal(result[1], expected2)
+
+        # For 'left' join on different axis
+        result = df.align(ts, join='left', axis=1, broadcast_axis=1)
+        expected1 = DataFrame(np.array([[1., 2.], [3., 4.]]),
+                              columns=list('AB'))
+        expected2 = DataFrame(np.array([[5., 5.], [6., 6.], [7., 7.]]),
+                              columns=list('AB'))
+        assert_frame_equal(result[0], expected1)
+        assert_frame_equal(result[1], expected2)
+
+        # Series.align(DataFrame) tests, 'outer' join
+        result = ts.align(df, join='outer', axis=0, broadcast_axis=1)
+        expected1 = DataFrame(np.array([[5., 5.], [6., 6.], [7., 7.]]),
+                              columns=list('AB'))
+        expected2 = DataFrame(np.array([[1., 2.], [3., 4.],
+                                        [pd.np.nan, pd.np.nan]]),
+                              columns=list('AB'))
+        assert_frame_equal(result[0], expected1)
+        assert_frame_equal(result[1], expected2)
+
+        # Series.align(DataFrame) tests, 'inner' join
+        result = ts.align(df, join='inner', axis=0, broadcast_axis=1)
+        expected1 = DataFrame(np.array([[5., 5.], [6., 6.]]),
+                              columns=list('AB'))
+        expected2 = DataFrame(np.array([[1., 2.], [3., 4.]]),
+                              columns=list('AB'))
+        assert_frame_equal(result[0], expected1)
+        assert_frame_equal(result[1], expected2)

pandas/tests/test_generic.py

@@ -1874,6 +1874,7 @@ def test_pipe_panel(self):
         with tm.assertRaises(ValueError):
             result = wp.pipe((f, 'y'), x=1, y=1)
 
+
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb', '--pdb-failure'],
                    exit=False)