[R] computing sum of indicator variables
Uwe Ligges
ligges at statistik.uni-dortmund.de
Mon Jul 26 11:00:02 CEST 2004
Stefan Böhringer wrote:
> My problem is as follows:
> i is a list
Do you mean a vector?
> of integers of variable length. Now I want to compute a new
> vector/array
A vector or an array (which dimensions?)?
> that contains 1's at the positions indicated in i. For
> example:
> c(2, 4) -> c(0, 1, 0, 1)
How long should the result be? max(i)???
If you mean simple vectors in both cases, i's suggest:
i <- c(2, 4)
x <- numeric(max(i))
x[i] <- 1
Uwe Ligges
> Using something like
> i = i - c(0, i[2:length(i) - 1]);
> sapply(i, function(x) c(rep(0, x - 1), 1)));
>
> faces me with the problem of concatenating the result, which I could
> somehow not find a solution for.
>
> Thank you very much in advance.
>
> Stefan
>
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