Is this what you want?
> x <- read.table(textConnection(" chrN start end
+ 1 chr1 11122333 11122633
+ 2 chr1 11122333 11122633
+ 3 chr3 11122333 11122633
+ 8 chr3 111273334 111273634
+ 7 chr2 12122334 12122634
+ 4 chr1 21122377 21122677
+ 5 chr2 33122355 33122655
+ 6 chr2 33122355 33122655"), header=TRUE)> x$count <- ave(x$start, x$start, FUN=length)
> x
chrN start end count
1 chr1 11122333 11122633 3
2 chr1 11122333 11122633 3
3 chr3 11122333 11122633 3
8 chr3 111273334 111273634 1
7 chr2 12122334 12122634 1
4 chr1 21122377 21122677 1
5 chr2 33122355 33122655 2
6 chr2 33122355 33122655 2
On 2/4/08, joseph <jdsandjd at yahoo.com> wrote:> Hi Peter
> I have the following data frame with chromosome name, start and end
positions:
> chrN start end
> 1 chr1 11122333 11122633
> 2 chr1 11122333 11122633
> 3 chr3 11122333 11122633
> 8 chr3 111273334 111273634
> 7 chr2 12122334 12122634
> 4 chr1 21122377 21122677
> 5 chr2 33122355 33122655
> 6 chr2 33122355 33122655
> I would like to count the positions that have the same start and add a new
column with the count number;
> the new data frame should look like this:
> chrN
> start end count
> 1 chr1 11122333 11122633 3
> 2 chr1 11122333 11122633 3
> 3 chr3 11122333 11122633 3
> 8 chr3 111273334 111273634 1
> 7 chr2 12122334 12122634 1
> 4 chr1 21122377 21122677 1
> 5 chr2 33122355 33122655 2
> 6 chr2 33122355 33122655 2
> Can you please show me how to achieve this?
> Thanks
> Joseph
>
>
>
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Jim Holtman
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What is the problem you are trying to solve?