Replace NAs with mean of the same column of a data.table

Question

I want to replace NAs present in a column of a DATA TABLE with the mean of the same column. I am doing the following. But it is not working.

ww <- data.ta         


        

Answer 1

While the zoo answer is pretty nice it requires new dependency.
Using just data.table you could do the following.

library(data.table)

# prepare data
ww = data.table(iris[1:5,])
ww[1, Sepal.Length := NA]

# solution
ww[, Sepal.Length.mean := mean(Sepal.Length, na.rm = TRUE) # calculate mean
   ][is.na(Sepal.Length), Sepal.Length := Sepal.Length.mean # replace NA with mean
     ][, Sepal.Length.mean := NULL # remove mean col
       ][] # just prints

While it may looks biggish comparing to zoo's, it is performance efficient as all steps are made using update by reference :=. It can also be easily tuned to replace NA with mean by group, just using by argument in data.table.