How to fill NAs with LOCF by factors in data frame, split by country

Question

I have the following data frame (simplified) with the country variable as a factor and the value variable has missing values:

country value
AUT     NA
AUT            


        

Answer 1

I'm a little late to this conversation, but here is a data.table way, which will be much faster for larger data sets:

library(zoo)
library(data.table)

# Convert to data table
setDT(data)

data[, value := na.locf(value, na.rm = FALSE), by = country]

data
   country  value
1:     AUT     NA
2:     AUT      5
3:     AUT      5
4:     AUT      5
5:     GER     NA
6:     GER     NA
7:     GER      7
8:     GER      7
9:     GER      7

# And if you want to convert "data" back to a data frame...
setDF(data)