Message-ID: <3A822319EB35174CA3714066D590DCD50205CBC9@usrymx25.merck.com>
Date: 2003-09-29T15:38:39Z
From: Liaw, Andy
Subject: can I have a matrix of factors, please?
Dear R-help,
Is it a violation of the S language to have a matrix of factors? What I
would like to have is just a factor object that has dim attribute, and can
be printed (and subsetted) like a matrix; i.e., all columns/rows have the
identical levels. However, I can't get it to work:
> x <- factor(sample(2, 10, replace=TRUE))
> dim(x)<- c(5,2)
> x
[1] 1 2 2 1 2 1 1 1 2 1
Levels: 1 2
> str(x)
int [1:5, 1:2] 1 2 2 1 ...
- attr(*, "levels")= chr [1:2] "1" "2"
- attr(*, "class")= chr "factor"
> x[1,]
factor(0)
Levels: 1 2
(This is R 1.7.1 on WinXPPro.)
The alternative is to have a list instead, where each "column" makes up a
component of the list. But it would be nice to have the matrix...
Best,
Andy
Andy Liaw, PhD
Biometrics Research PO Box 2000, RY33-300
Merck Research Labs Rahway, NJ 07065
mailto:andy_liaw at merck.com 732-594-0820