[R] newbie question about index

[Gabor Grothendieck]

Try using outer:

outer(1:3, a, "==")+0




On 8/31/06, z s <flyhyena at yahoo.com.cn> wrote:
> Hi,
>
>  I am trying to convert a variable a = sample(1:3,100,rep = T) represents choices into a 3X100 dummy varible b with corresponding element set to 1 otherwise 0.
> eg.
>
> a: 1 3 2 1 2 3 1 1....
>
> b: 1 0 0 1 0 0 1 1..
>    0 0 1 0 1 0 0 0...
>    0 1 0 0 0 1 0 0...
>
>  Is there something like b[a] =1 existing? I could not figure this out myself.
>
>
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