From fb3f8963f29f7eb2d4465ec11e9b5fb70aadbb79 Mon Sep 17 00:00:00 2001
From: Alessandro Sivieri <alessandro.sivieri@gmail.com>
Date: Thu, 10 Nov 2016 17:18:15 +0100
Subject: [PATCH] Patching issue number 14615 - optional arguments for
 functions in resample.

---
 pandas/tseries/resample.py            | 16 +++++++++++++---
 pandas/tseries/tests/test_resample.py | 11 +++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/pandas/tseries/resample.py b/pandas/tseries/resample.py
index d02c403cb3c66..c2cb637708287 100644
--- a/pandas/tseries/resample.py
+++ b/pandas/tseries/resample.py
@@ -319,9 +319,19 @@ def aggregate(self, arg, *args, **kwargs):
         self._set_binner()
         result, how = self._aggregate(arg, *args, **kwargs)
         if result is None:
-            return self._groupby_and_aggregate(arg,
-                                               *args,
-                                               **kwargs)
+            # It seems there is an ambiguity in having both named args
+            # and variadic in the same function, so we need to distinguish here,
+            # otherwise the first element of args is "eaten" by grouper in
+            # _groupby_and_aggregate.
+            if len(args) == 0:
+                return self._groupby_and_aggregate(arg,
+                                                   *args,
+                                                   **kwargs)
+            else:
+                return self._groupby_and_aggregate(arg,
+                                                   None,
+                                                   *args,
+                                                   **kwargs)
 
         return result
 
diff --git a/pandas/tseries/tests/test_resample.py b/pandas/tseries/tests/test_resample.py
index 9d3d27f3224b4..19ed97c4a9079 100644
--- a/pandas/tseries/tests/test_resample.py
+++ b/pandas/tseries/tests/test_resample.py
@@ -2039,6 +2039,17 @@ def test_resample_datetime_values(self):
         res = df['timestamp'].resample('2D').first()
         tm.assert_series_equal(res, exp)
 
+    def test_resample_additional_args(self):
+        # Issue 14615
+        
+        rng = date_range('1/1/2011', periods = 72, freq = 'H')
+        rng_exp = date_range('1/1/2011', periods = 3, freq = 'D')
+        vals = np.tile(np.arange(0, 24), 3)
+        ts = Series(vals, index = rng)
+        ts_exp = Series([286, 286, 286], index = rng_exp)
+        res = ts.resample("D").apply(lambda x, y: np.sum(x) + y, 10)
+        tm.assert_series_equal(res, ts_exp)
+
 
 class TestPeriodIndex(Base, tm.TestCase):
     _multiprocess_can_split_ = True