How to fill NA with median?

Question

Example data:

set.seed(1)
df <- data.frame(years=sort(rep(2005:2010, 12)), 
                 months=1:12, 
                 value=c(rnorm(60),NA,NA,NA,NA,         


        

Answer 1

Sticking with base R, you can also try the following:

medians = sapply(split(df[1:60, 3], df[1:60, 2]), median)
df[61:72, 3] = medians