Taking a data.table slice with a sequence of (row,col) indices

Question

I have a data.table that resembles the one below.

tab <- data.table(a = c(NA, 42190, NA), b = c(42190, 42190, NA), c = c(40570, 42190, NA))
tab
          


        

Answer 1

There is a faster way to do this than coercing to either matrix or data.frame. Just use the [data.frame function.

`[.data.frame`( tab,  cbind(ri,ci) )
[1]    NA 42190    NA

This is the functional syntax for the [.data.frame function.