hi:
here is one solution:

cat<-as.factor(c(1,1,3,2,4))
model.matrix(~cat-1,cat)

cbind(cat,model.matrix(~cat-1,cat))
Andrija

On Tue, Apr 12, 2011 at 2:17 PM, Shane Phillips <SPhillips@lexington1.net>wrote:

> I have a categorical variable in a dataframe similar to the following...
>
> cat
> 1
> 1
> 3
> 2
> 4
>
> I need to convert it to 4 dichotemous variables for each observations
> like...
>
> cat1    cat2    cat3    cat4
> 1       0       0       0
> 1       0       0       0
> 0       0       1       0
> 0       1       0       0
> 0       0       0       1
>
>
> Thanks in advance!
>
> Shane
>
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> and provide commented, minimal, self-contained, reproducible code.
>

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