How to remove multiple columns every nth column in R?

Question

So I have a dataframe with an unspecified number of columns (all I know is there would be at least 4 columns).

What I want to do is, for every 4 columns, I want to delete columns 3 and 4.

So let's say my dataframe contains 12 columns. In that case, I want to delete columns 3, 4, 7, 8, 11, 12.

I know that I can delete a column every nth column like this:

df <- df[,seq(2,ncol(df),4)]

But how can I delete every 3rd and 4th column in the same way using R?

Thank you.

Answer 1

As these are index, use - to remove those columns

i1 <- rep(seq(3, ncol(df), 4) , each = 2) + 0:1
df[,-i1]

Or another option is to use a logical index to recycle

df[!c(FALSE, FALSE, TRUE, TRUE)]

data

set.seed(24)
df <- as.data.frame(matrix(rnorm(12 * 4), 4, 12))