[R] Number of replications of a term

Liaw, Andy andy_liaw at merck.com
Tue Jan 24 18:37:23 CET 2006

```This should work:

> ids <- c( "ID1", "ID2", "ID2", "ID3", "ID3","ID3", "ID5")
> table(ids)[ids]
ids
ID1 ID2 ID2 ID3 ID3 ID3 ID5
1   2   2   3   3   3   1

Andy

From: Laetitia Marisa
>
> Hello,
>
> Is there a simple and fast function that returns a vector of
> the number
> of replications for each object of a vector ?
> For example :
> I have a vector of IDs :
> ids <- c( "ID1", "ID2", "ID2", "ID3", "ID3","ID3", "ID5")
>
>  I want the function returns the following vector where each
> term is the
> number of replicates for the given id :
> c( 1, 2, 2, 3,3,3,1 )
>
> Of course I have a vector of more than 40 000 ID and the function I
> wrote (it orders my data and checks on ID:Name of the data if
> the next
> term is the same as the previous one (see below) ) is really slow
> (30minutes for 44290 terms). But I don't have time by now to
> write a C
> function.
> Thanks a lot for your help,
>
> Laetitia.
>
>
>
> Here is the function I have written maybe I have done something not
> optimized :
>
> repVector <- function(obj){
>
>     # order IDName
>     ord <- gif.indexByIDName(obj)
>     ordobj <- obj[ord,]
>
>     nspots <- nrow(obj)
>     # vector of spot replicates number
>     spotrep <- rep(NA, nspots )
>
>     # function to get ID:Name for a given spot
>     spotidname <- function(ind){
>             paste(ordobj\$genes[ind, c("ID","Name") ], collapse=":")
>     }
>
>     spot <- 1
>
>     while( spot < nspots ){
>         i<-1
>         while( spotidname(spot) == spotidname(spot + i) ){
>
>             i <- i + 1
>         }
>
>         spotrep[spot : (spot + i-1)] <- i
>         spot <- spot + i
>         #cat("spot : ",spot,"\n")
>     }
>
>     obj\$genes\$spotrep <- spotrep[order(ord)]
>
>     obj
>
> }
>
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