pythonpandasdatetime

TypeError: Index.reindex() got an unexpected keyword argument ‘fill_value'

I am trying to get the indices of the missing date by comparing it to a list of un-missed dates, as the following:

a = pd.DatetimeIndex(["2000", "2001", "2002", "2003",
                      "2004", "2005", "2009", "2010"])
b = pd.DatetimeIndex(["2000", "2001", "2002", "2003",
                      "2004", "2005", "2006", "2007",
                      "2008", "2009", "2010"])
a.reindex(b)

I got the following

(DatetimeIndex(['2000-01-01', '2001-01-01', '2002-01-01', '2003-01-01',
                '2004-01-01', '2005-01-01', '2006-01-01', '2007-01-01',
                '2008-01-01', '2009-01-01', '2010-01-01'],
               dtype='datetime64[ns]', freq=None),
 array([ 0,  1,  2,  3,  4,  5, -1, -1, -1,  6,  7]))

I tried to replace all missing value which is -1 to Nan, by using a.reindex(b, fill_value=np.NAN) but I got the following error TypeError: Index.reindex() got an unexpected keyword argument ‘fill_value’

According the pandas documentation fill_vaue is among the parameters of reindex. Any ideas?

Solution

  • First of all, you have to do:

    newIndex, indexer = a.reindex(b)

    reindex returns two things. You need/want to get only the indexer.

    So now you can get what you want:

    indexerWithNan = np.where(indexer == -1, np.nan, indexer)

    Which is:

    [ 0.  1.  2.  3.  4.  5. nan nan nan  6.  7.]

    Why was your initial code wrong? The reindex() method does not support the fill_value parameter for pandas.Index objects as it does for pandas.Series or pandas.DataFrame.