i have 2 df's ,in df1 we have NA values which needs to be replaced with mean of previous 2 years Average_f1 eg. in df1 - for row 5 year is 2015 and bin - 5 and we need to replace previous 2 years mean for same bin from df2 (2013&2014) and for row-7 we have only 1 year value
df1 df2
year p1 bin year bin_p1 Average_f1
2013 20 1 2013 5 29.5
2013 24 1 2014 5 16.5
2014 10 2 2015 NA 30
2014 11 2 2016 7 12
2015 NA 5
2016 10 3
2017 NA 7
output
df1
year p1 bin
2013 20 1
2013 24 1
2014 10 2
2014 11 2
2015 **23** 5
2016 10 3
2017 **12** 7
Thanks in advance