[R] How to get row numbers of a subset of rows

[Julian Burgos]

One way to do this is

range(which(B[,2]==1))

Julian

affy snp wrote:
> Hello list,
> 
> I read in a txt file using
> 
> <B<-read.table(file="data.snp",header=TRUE,row.names=NULL)
> 
> by specifying the row.names=NULL so that the rows are numbered.
> Below is an example after how the table looks like using
> <B[1:10,1:3]
> 
> 
>       SNP                Chromosome  PhysicalPosition
> 1 SNP_A-1909444          1           7924293
> 2 SNP_A-2237149          1           8173763
> 3 SNP_A-4303947          1           8191853
> 4 SNP_A-2236359          1           8323433
> 5 SNP_A-2205441          1           8393263
> 6 SNP_A-1909445          1           7924293
> 7 SNP_A-2237146          2           8173763
> 8 SNP_A-4303946          2           8191853
> 9 SNP_A-2236357          2           8323433
> 10 SNP_A-2205442         2           8393263
> 
> I am wondering if there is a way to return the start and end row numbers
> for a subset of rows.
> 
> For example, If I specify B[,2]=1, I would like to get
> start=1 and end=6
> 
> if B[,2]=2, then start=7 and end=10
> 
> Is there any way in R to quickly do this?
> 
> Thanks a bunch!
> 
> Allen
> 
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