# [R] Number of replications of a term

Thomas Lumley tlumley at u.washington.edu
Tue Jan 24 19:06:17 CET 2006

```Ah. It's a bit more complicated than just table(), because you want the
result to be the same length.

tt <- table(id)
tt[match(id,names(tt))]

-thomas

On Tue, 24 Jan 2006, Laetitia Marisa wrote:

> 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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Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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