[R] multiple match question

[Marc Mamin]

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))))

Thanks for any help,

Marc