Replace NA values with median by group

Question

I have used the below tapply function to get the median of Age based on Pclass.

Now how can I impute those median values to NA values based on Pclass?

Answer 1

Try the following.

set.seed(1)
df1 <- data.frame(Pclass = sample(1:3, 20, TRUE),
                  Age = sample(c(NA, 20:40), 20, TRUE, prob = c(10, rep(1, 21))))

new <- ave(df1$Age, df1$Pclass, FUN = function(x) median(x, na.rm = TRUE))
df1$Age[is.na(df1$Age)] <- new[is.na(df1$Age)]

Final clean up.

rm(new)