BUG: fix closed='left' erroneous resampling logic regression. close #3020

Author: wesm

RELEASE.rst

@@ -194,13 +194,15 @@ pandas 0.11.0
   - Substitute warning for segfault when grouping with categorical grouper
     of mismatched length (GH3011_)
   - Fix exception in SparseSeries.density (GH2083_)
+  - Fix upsampling bug with closed='left' and daily to daily data (GH3020_)
 
 .. _GH2758: https://github.com/pydata/pandas/issues/2758
 .. _GH2809: https://github.com/pydata/pandas/issues/2809
 .. _GH2810: https://github.com/pydata/pandas/issues/2810
 .. _GH2837: https://github.com/pydata/pandas/issues/2837
 .. _GH2898: https://github.com/pydata/pandas/issues/2898
 .. _GH3035: https://github.com/pydata/pandas/issues/3035
+.. _GH3020: https://github.com/pydata/pandas/issues/3020
 .. _GH2978: https://github.com/pydata/pandas/issues/2978
 .. _GH2877: https://github.com/pydata/pandas/issues/2877
 .. _GH2739: https://github.com/pydata/pandas/issues/2739

pandas/tseries/resample.py

@@ -209,7 +209,13 @@ def _resample_timestamps(self, obj):
             else:
                 # upsampling shortcut
                 assert(self.axis == 0)
-                result = obj.reindex(binner[1:], method=self.fill_method,
+
+                if self.closed == 'right':
+                    res_index = binner[1:]
+                else:
+                    res_index = binner[:-1]
+
+                result = obj.reindex(res_index, method=self.fill_method,
                                      limit=self.limit)
         else:
             # Irregular data, have to use groupby

pandas/tseries/tests/test_resample.py

@@ -559,11 +559,11 @@ def test_resample_median_bug_1688(self):
             result = df.resample("T", how=lambda x: x.mean())
             exp = df.asfreq('T')
             tm.assert_frame_equal(result, exp)
-            
+
             result = df.resample("T", how="median")
             exp = df.asfreq('T')
             tm.assert_frame_equal(result, exp)
-            
+
     def test_how_lambda_functions(self):
         ts = _simple_ts('1/1/2000', '4/1/2000')
 
@@ -983,6 +983,14 @@ def test_all_values_single_bin(self):
         result = s.resample("A", how='mean')
         tm.assert_almost_equal(result[0], s.mean())
 
+    def test_resample_doesnt_truncate(self):
+        """Test for issue #3020"""
+        import pandas as pd
+        dates = pd.date_range('01-Jan-2014','05-Jan-2014', freq='D')
+        series = Series(1, index=dates)
+
+        result = series.resample('D')
+        self.assertEquals(result.index[0], dates[0])
 
 class TestTimeGrouper(unittest.TestCase):