Fill in missing values in pandas dataframe using mean
问题 datetime 2012-01-01 125.5010 2012-01-02 NaN 2012-01-03 125.5010 2013-01-04 NaN 2013-01-05 125.5010 2013-02-28 125.5010 2014-02-28 125.5010 2016-01-02 125.5010 2016-01-04 125.5010 2016-02-28 NaN I would like to fill in the missig values in this dataframe by using a climatology computed from the dataset i.e fill in missing 28th feb 2016 value by averaging values of 28th feb from other years. How do i do this? 回答1: You can use groupby by month and day and transform with fillna mean: print df