[R] "Glueing" factors together

[Dimitris Rizopoulos]

Dear Ted,

you could try something like,

dat <- data.frame(V1=sample(LETTERS[1:3], 10, rep=T),
V2=sample(letters[1:3], 10, rep=T))
mat <- apply(as.matrix(dat), 1, function(x) paste(x, collapse=""))
dat$glue <- factor(mat)
dat

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: "Ted Harding" <Ted.Harding at nessie.mcc.ac.uk>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, June 15, 2004 10:26 AM
Subject: [R] "Glueing" factors together


> Hi folks,
>
> Suppose I have a series of cases each with categorical
> factors A, B.
>
> What is the best way to "glue" A and B together into a single
> factor? For example, given
>
> A0 B1 ...
> A1 B1 ...
> A0 B2 ...
> A1 B0 ...
> A0 B0 ...
> A1 B2 ...
>
> then I'd like to end up with a single factor with levels
>
>   A0B0, A0B1, A0B2, A1B0, A1B1, A1B2
>
> according to all the combinations which actually occur in the
> data (e.g. if (A1,B2) did not occur in the data, then A1B2 would
> not be a level in the resulting "glued" factor).
>
> I can see clumsy and tedious ways involving manipulating strings,
> paste(), etc.; but I'm sure it must be possible more elegantly.
>
> With thanks, and best wishes to all,
> Ted.
>
>
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <Ted.Harding at nessie.mcc.ac.uk>
> Fax-to-email: +44 (0)870 167 1972
> Date: 15-Jun-04                                       Time: 09:26:06
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