ENH: add fill_value to asfreq pandas-dev#14591

Author: nchmura4

pandas/core/generic.py

@@ -3990,7 +3990,7 @@ def groupby(self, by=None, axis=0, level=None, as_index=True, sort=True,
                        sort=sort, group_keys=group_keys, squeeze=squeeze,
                        **kwargs)
 
-    def asfreq(self, freq, method=None, how=None, normalize=False):
+    def asfreq(self, freq, method=None, how=None, normalize=False, fill_value=None):
         """
         Convert TimeSeries to specified frequency.
 
@@ -4021,7 +4021,7 @@ def asfreq(self, freq, method=None, how=None, normalize=False):
         <http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
         """
         from pandas.tseries.resample import asfreq
-        return asfreq(self, freq, method=method, how=how, normalize=normalize)
+        return asfreq(self, freq, method=method, how=how, normalize=normalize, fill_value=fill_value)
 
     def at_time(self, time, asof=False):
         """
@@ -4067,7 +4067,7 @@ def between_time(self, start_time, end_time, include_start=True,
 
     def resample(self, rule, how=None, axis=0, fill_method=None, closed=None,
                  label=None, convention='start', kind=None, loffset=None,
-                 limit=None, base=0, on=None, level=None, fill_value=None):
+                 limit=None, base=0, on=None, level=None):
         """
         Convenience method for frequency conversion and resampling of time
         series.  Object must have a datetime-like index (DatetimeIndex,
@@ -4102,11 +4102,6 @@ def resample(self, rule, how=None, axis=0, fill_method=None, closed=None,
 
             .. versionadded:: 0.19.0
 
-        fill_value: scalar, optional
-            Value to use for missing values, applied before resampling
-
-            .. version added:: 0.20.0
-
         To learn more about the offset strings, please see `this link
         <http://pandas.pydata.org/pandas-docs/stable/timeseries.html#offset-aliases>`__.
 
@@ -4211,10 +4206,6 @@ def resample(self, rule, how=None, axis=0, fill_method=None, closed=None,
         from pandas.tseries.resample import (resample,
                                              _maybe_process_deprecations)
         axis = self._get_axis_number(axis)
-
-        if(fill_value is not None):
-            self = self.fillna(fill_value)
-
         r = resample(self, freq=rule, label=label, closed=closed,
                      axis=axis, kind=kind, loffset=loffset,
                      convention=convention,

pandas/tseries/resample.py

@@ -499,12 +499,12 @@ def interpolate(self, method='linear', axis=0, limit=None, inplace=False,
                                   limit_direction=limit_direction,
                                   downcast=downcast, **kwargs)
 
-    def asfreq(self):
+    def asfreq(self, **kwargs):
         """
         return the values at the new freq,
         essentially a reindex with (no filling)
         """
-        return self._upsample('asfreq')
+        return self._upsample('asfreq', **kwargs)
 
     def std(self, ddof=1, *args, **kwargs):
         """
@@ -704,7 +704,7 @@ def _adjust_binner_for_upsample(self, binner):
             binner = binner[:-1]
         return binner
 
-    def _upsample(self, method, limit=None):
+    def _upsample(self, method, limit=None, fill_value=None):
         """
         method : string {'backfill', 'bfill', 'pad',
             'ffill', 'asfreq'} method for upsampling
@@ -736,7 +736,7 @@ def _upsample(self, method, limit=None):
             result.index = res_index
         else:
             result = obj.reindex(res_index, method=method,
-                                 limit=limit)
+                                 limit=limit, fill_value=fill_value)
 
         return self._wrap_result(result)
 
@@ -1333,7 +1333,7 @@ def _adjust_dates_anchored(first, last, offset, closed='right', base=0):
             Timestamp(lresult).tz_localize(last_tzinfo, ambiguous=last_dst))
 
 
-def asfreq(obj, freq, method=None, how=None, normalize=False):
+def asfreq(obj, freq, method=None, how=None, normalize=False, fill_value=None):
     """
     Utility frequency conversion method for Series/DataFrame
     """
@@ -1353,7 +1353,7 @@ def asfreq(obj, freq, method=None, how=None, normalize=False):
             return obj.copy()
         dti = date_range(obj.index[0], obj.index[-1], freq=freq)
         dti.name = obj.index.name
-        rs = obj.reindex(dti, method=method)
+        rs = obj.reindex(dti, method=method, fill_value=fill_value)
         if normalize:
             rs.index = rs.index.normalize()
         return rs