[R] how to combine apply and which or alternative ways to do so

[arun]

HI,
May be this helps:

set.seed(24)
 vec1<- sample(1e5,1e4,replace=FALSE)
 set.seed(48)
 vec2<- sample(1e7,1e6,replace=FALSE)
 system.time(res<- sapply(vec1,function(x) which(vec2%in%x)))
#   user  system elapsed 
#212.520   0.500 213.386 

#or
system.time({res2<- match(vec1,vec2) #assuming that there are no duplicate elements
         res3<- res2[!is.na(res2)]})
# user  system elapsed 
#  0.044   0.000   0.044 
identical(unlist(res),res3)
#[1] TRUE

A.K.


----- Original Message -----
From: Guillaume Bal <balguillaume2883 at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Friday, August 23, 2013 5:37 PM
Subject: [R] how to combine apply and which or alternative ways to do so

Dear useRs,

I am currently doing some data cleaning and data manipulation and I have the
following problem.
I have two vectors. Let say the size of the first one is 10 000 (vector 1)
and the size of the second one is 1 000 000 (vector 2).

I need to know for each cell of vector 1 which cells of vector 2 correspond.

I tried to combine the "which" and "apply"  but I dit not succeed and  I
have no idea about a possible vectorization.

Can someone help me ?

Thanks

Guillaume

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