Merge pull request #10053 from jnmclarty/doc_infer_freq

DOC: Add infer frequency to docs

Author: jreback

doc/source/api.rst

@@ -158,6 +158,7 @@ Top-level dealing with datetimelike
    bdate_range
    period_range
    timedelta_range
+   infer_freq
 
 Top-level evaluation
 ~~~~~~~~~~~~~~~~~~~~
@@ -1364,6 +1365,7 @@ Time/Date Components
    DatetimeIndex.is_quarter_end
    DatetimeIndex.is_year_start
    DatetimeIndex.is_year_end
+   DatetimeIndex.inferred_freq
 
 Selecting
 ~~~~~~~~~
@@ -1414,6 +1416,7 @@ Components
    TimedeltaIndex.microseconds
    TimedeltaIndex.nanoseconds
    TimedeltaIndex.components
+   TimedeltaIndex.inferred_freq
 
 Conversion
 ~~~~~~~~~~

pandas/tseries/base.py

@@ -79,6 +79,11 @@ def freqstr(self):
 
     @cache_readonly
     def inferred_freq(self):
+        """ 
+        Trys to return a string representing a frequency guess, 
+        generated by infer_freq.  Returns None if it can't autodetect the 
+        frequency.
+        """
         try:
             return infer_freq(self)
         except ValueError:

pandas/tseries/frequencies.py

@@ -671,11 +671,11 @@ def _period_str_to_code(freqstr):
 def infer_freq(index, warn=True):
     """
     Infer the most likely frequency given the input index. If the frequency is
-    uncertain, a warning will be printed
+    uncertain, a warning will be printed. 
 
     Parameters
     ----------
-    index : DatetimeIndex
+    index : DatetimeIndex or TimedeltaIndex
             if passed a Series will use the values of the series (NOT THE INDEX)
     warn : boolean, default True
 
@@ -684,6 +684,7 @@ def infer_freq(index, warn=True):
     freq : string or None
         None if no discernible frequency
         TypeError if the index is not datetime-like
+        ValueError if there are less than three values.
     """
     import pandas as pd