Fill missing value based on probability of occurrence

Question

This is what my data.table/dataframe looks lke

library(data.table)
dt <- fread(\'
   STATE     ZIP      
   PA        19333        
   PA        19327                 


        

Answer 1

Here's a way just using sample, wrapped up in a convenience function.

sample_fill_na = function(x) {
    x_na = is.na(x)
    x[x_na] = sample(x[!x_na], size = sum(x_na), replace = TRUE)
    return(x)
}

dt[, ZIP := sample_fill_na(ZIP), by = STATE]