CODEWITHSUNDEEP
rdatatable
Mahmoud
Mahmoud

Reputation: 401

R change datatable factor levels using column index

Assume a datatable DT below

DT <- data.table(m=1:3, n=factor(c("a","b","c")))

I would like to change the levels of the 2nd column to c("d","e","f"). I can do it using

levels(DT$n) <- c("d","e","f")

But, what should I do if I just know the column index; i.e. 2. I tried the following line but it doesn't work!

i=2
levels(DT[, ..i]) <- c("d","e","f")

This is the error I get:

Error in `[<-.data.table`(`*tmp*`, , ..i, value = list(n = 1:3)) : object '..i' not found

Upvotes: 0

Views: 133

Answers (1)

MKa
MKa

Reputation: 2318

You could still do data.frame way:

levels(DT[[2]]) <- c("d", "e", "f")

Note however it is usually not recommended to update by column index though..

Upvotes: 1

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