Replace NA with previous and next rows mean in R

Question

How could I Replace a NA with mean of its previous and next rows in a fast manner?

  name grade
1    A    56
2    B    NA
3    C    70
4    D    96
         


        

Answer 1

Assume you have a data.frame df like this:

> df
  name grade
1    A    56
2    B    NA
3    C    70
4    D    96
5    E    NA
6    F    95

Then you can use the following:

> ind <- which(is.na(df$grade))
> df$grade[ind] <- sapply(ind, function(i) with(df, mean(c(grade[i-1], grade[i+1]))))
> df
  name grade
1    A    56
2    B    63
3    C    70
4    D    96
5    E  95.5
6    F    95