REF: starting to refactor for removing LongPanel, GH #108

Author: wesm

RELEASE.rst

@@ -98,10 +98,10 @@ Thanks
 ------
 - Craig Austin
 - Andreas Hilboll
-- Adam Klein
 - Matt Harrison
 - Mario Gamboa-Cavazos
 - Arthur Gerigk
+- Adam Klein
 - Gregg Lind
 - Solomon Negusse
 - Wouter Overmeire

pandas/core/api.py

@@ -10,7 +10,7 @@
 from pandas.core.daterange import DateRange
 from pandas.core.series import Series, TimeSeries
 from pandas.core.frame import DataFrame
-from pandas.core.panel import Panel, LongPanel
+from pandas.core.panel import Panel
 from pandas.core.groupby import groupby
 from pandas.core.reshape import pivot_simple as pivot
 

pandas/core/frame.py

@@ -2484,31 +2484,12 @@ def _apply_broadcast(self, func, axis):
 
         return result
 
-    def _apply_level(self, f, axis='major', broadcast=False):
-        from pandas.core.panel import LongPanel
-
-        if axis == 'major':
-            panel = self.swapaxes()
-            result = panel._apply_level(f, axis='minor', broadcast=broadcast)
-            if broadcast:
-                result = result.swapaxes()
-
-            return result
-
-        bounds = self.index._bounds
-        values = self.values
-        N, _ = values.shape
-        result = group_agg(values, bounds, f)
-
+    def _apply_level(self, f, level=0, broadcast=False):
+        grouped = self.groupby(level=level)
         if broadcast:
-            repeater = np.concatenate((np.diff(bounds), [N - bounds[-1]]))
-            panel = LongPanel(result.repeat(repeater, axis=0),
-                              columns=self.items, index=self.index)
+            return grouped.transform(f)
         else:
-            panel = DataFrame(result, index=self.major_axis,
-                              columns=self.items)
-
-        return panel
+            return grouped.agg(f)
 
     def applymap(self, func):
         """