BUG: Fixed NDFrame.transform('abs')

Closes pandas-dev#19760

Author: TomAugspurger

pandas/core/apply.py

@@ -111,7 +111,9 @@ def get_result(self):
 
         # string dispatch
         if isinstance(self.f, compat.string_types):
-            self.kwds['axis'] = self.axis
+            if self.f not in {'abs'}:
+                # Not all transform functions take an axis keyword.
+                self.kwds['axis'] = self.axis
             return getattr(self.obj, self.f)(*self.args, **self.kwds)
 
         # ufunc

pandas/tests/frame/test_apply.py

@@ -880,6 +880,13 @@ def f():
             with np.errstate(all='ignore'):
                 df.agg({'A': ['abs', 'sum'], 'B': ['mean', 'max']})
 
+    def test_transform_abs_name(self):
+        # https://github.com/pandas-dev/pandas/issues/19760
+        df = pd.DataFrame({"A": [-1, 2]})
+        result = df.transform('abs')
+        expected = pd.DataFrame({"A": [1, 2]})
+        tm.assert_frame_equal(result, expected)
+
     def test_demo(self):
         # demonstration tests
         df = pd.DataFrame({'A': range(5), 'B': 5})