[R] multiple match question

[Uwe Ligges]

Marc Mamin wrote:

> Hello,
> 
>  I'm looking for a fast way to retrieve the position of elements  from a vector which match element in another vector.
> 
> Example
> 
> va<-c('a','e')
> vb<-c('a','b','c','d','e','f','e')
> 
> f(va,vb) should return c(1,5,7)
> 
> I have 2 different cases: 
> 
> I) my vector vb contains only distinct values
> II) my vector vb may contains the same values more than once.
> 
> for I) I use following which is fast enough:
> 
> 	as.vector(na.omit(unlist(lapply(va,match,vb))))


  which(vb %in% va)

Uwe Ligges


> Thanks for any help,
> 
> Marc
> 
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