jnam27 jnam27 - 6 months ago 23
R Question

How to replace NA values in a table *for selected columns*? data.frame, data.table

There are a lot of posts about replacing NA values. I am aware that one could replace NAs in the following table/frame with the following:


But, what if I want to restrict it to only certain columns? Let's me show you an example.

First, let's start with a dataset.

x <- data.frame(a=sample(c(1,2,NA), 10, replace=T),
b=sample(c(1,2,NA), 10, replace=T),
c=sample(c(1:5,NA), 10, replace=T))

Which gives:

a b c
1 1 NA 2
2 2 2 2
3 2 1 1
4 2 NA 1
5 NA 1 2
6 2 NA 5
7 1 1 4
8 1 1 NA
9 2 1 5
10 2 1 1

Ok, so I only want to restrict the replacement to columns 'a' and 'b'. My attempt was:

x[is.na(x), 1:2]<-0



Which does not work.

My data.table attempt, where
, was obviously never going to work:

y[is.na(y[,list(a,b)]), ]

I want to pass columns inside the is.na argument but that obviously wouldn't work.

I would like to do this in a data.frame and a data.table. My end goal is to recode the 1:2 to 0:1 in 'a' and 'b' while keeping 'c' the way it is, since it is not a logical variable. I have a bunch of columns so I don't want to do it one by one. And, I'd just like to know how to do this.

Do you have any suggestions?


You can do:

x[, 1:2][is.na(x[, 1:2])] <- 0

or better (IMHO), use the variable names:

x[c("a", "b")][is.na(x[c("a", "b")])] <- 0

In both cases, 1:2 or c("a", "b") can be replaced by a pre-defined vector.