How to handle missing values in R by replacing it with mean? [closed]

Answer 1

There will be tons of ways to do this. The library zoo has a built in function na.aggregate which does precisely what you want.

library(zoo)
d <- data.frame(key = rep(c("key1", "key2"), each = 3), 
    value = c(10, 12, NA, 2, 3, NA))  
with(d, na.aggregate(value, by = key))