You could try this:

i <- c(5, 8)
a <- list(a1, a2, a3, a4)
subset(stack(as.data.frame(sapply(a, '[', 1:max(sapply(a, length))))),
       values %in% i, ind)

On Thu, Jun 17, 2010 at 8:40 PM, song song <rprojecthelp@gmail.com> wrote:

> for example, I have
>
> a1=c(1,3,5)
> a2=c(2,4,6)
> a3=c(7,8)
> a4=c(9,10)
>
> now if I have i=5, so i in a1, then I get a feedback tag[5]=1
>                   i=8,  so i in a3, then can get tag[8]=3
>
> in there any function to do this to check the element belongs to which
> group?
>
> thank you!!!
>
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>
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>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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