[R] computing sum of indicator variables

[Dimitris Rizopoulos]

Hi Stefan,

you could try something like,

x <- c(2,4,7)
as.numeric(!is.na(match(seq(1, max(x)), x)))

I hope this helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Doctoral Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/16/396887
Fax: +32/16/337015
Web: http://www.med.kuleuven.ac.be/biostat/
     http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Stefan Böhringer" <commercial at s-boehringer.de>
To: "R Help" <r-help at stat.math.ethz.ch>
Sent: Monday, July 26, 2004 10:45 AM
Subject: [R] computing sum of indicator variables


> My problem is as follows:
> i is a list of integers of variable length. Now I want to compute a
new
> vector/array that contains 1's at the positions indicated in i. For
> example:
> c(2, 4) -> c(0, 1, 0, 1)
>
> 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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