The column looks like Mod_month Mod_year Reg_Year Reg_Month 10 2016 2016 10 1 2018 2016 12 2 2017 2017 2 I want to perform some mathematical operations on columns of a dataframe to calculate difference between dates. I've tried using: df['difference']=df[df['mod_month']-df['last_month']+df['mod_month']*12-df['last_year']] But I get this error: KeyError: '[-1896 -2015 -1993 ... -1955 -1877 -1981] not in index' Which I think is due to null values, I also tried using coerce = 'True', which returns invalid syntax. I have seen other posts, but none of them has the error that I have, therefore any help would be appreciated. Continue reading...
