[R] Coding categorical -> dummy

Samir Messad messad at cirad.cirad.fr
Wed May 9 17:59:40 CEST 2001

Dear R-Users,

I have a data frame with several categorical variables. I want to code
these variables in dummy variables keeping all levels.
I know the function model.matrix (see below) but it works only for one
categorical variable :

> tt <- c("a","a","b","a","c")
> tt <- factor(tt)
> model.matrix(~ tt - 1)

Is there anyone who have write such function ?
Thanks for your help.

Samir Messad

Samir Messad    E-Mail : messad at cirad.fr
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