fixed asfreq in Resampler.asfreq using TDI

Author: discort

doc/source/whatsnew/v0.24.0.txt

@@ -703,6 +703,7 @@ Groupby/Resample/Rolling
 - Multiple bugs in :func:`pandas.core.Rolling.min` with ``closed='left'` and a
   datetime-like index leading to incorrect results and also segfault. (:issue:`21704`)
 - Bug in :meth:`Resampler.apply` when passing postiional arguments to applied func (:issue:`14615`).
+- Bug in :meth:`Resampler.asfreq` when frequency of ``TimedeltaIndex`` is a subperiod of a new frequency (:issue:`13022`).
 
 Sparse
 ^^^^^^

pandas/core/resample.py

@@ -1158,7 +1158,7 @@ def _adjust_binner_for_upsample(self, binner):
         """ adjust our binner when upsampling """
         ax = self.ax
 
-        if is_subperiod(ax.freq, self.freq):
+        if is_subperiod(ax.freq, self.freq) and ax.freq <= self.freq:
             # We are actually downsampling
             # but are in the asfreq path
             # GH 12926

pandas/tests/test_resample.py

@@ -2939,6 +2939,14 @@ def test_resample_with_nat(self):
                                                    freq='1S'))
         assert_frame_equal(result, expected)
 
+    def test_resample_as_freq_with_subperiod(self):
+        # GH 13022
+        index = pd.timedelta_range('00:00:00', '00:10:00', freq='5T')
+        df = DataFrame(data=[[1, 3], [-5, 10], [0, 0]], index=index)
+        result = df.resample('1T').asfreq()
+        expected = df.resample('1T').mean()
+        assert len(result) == len(expected)
+
 
 class TestResamplerGrouper(object):