Hi:

Using the plyr package,

summarise(dd, b = b, wx = (w + x)/2, yz = (y + z)/2)
      b wx  yz
1  chr2  6 4.5
2  chr1  7 2.0
3  chrY  8 5.0
4 chr13  9 5.5
5  chrX 10 7.5

HTH,
Dennis

On Sun, Jun 6, 2010 at 9:53 PM, Yuan Jian <jayuan2008@yahoo.com> wrote:

> Hi R experts.
>
> how can I average two sets of columns?
>
> dd <- data.frame(b = c("chr2", "chr1", "chrY", "chr13", "chrX"),
>       w=11:15, x = 1:5, y = c(8, 3, 9, 9,7),
>        z = c(1, 1, 1, 2, 8))
> expected result for mean(w,x) and mean(y,z) is
> 1  chr2 6  4.5
> 2  chr1 7  2
> 3  chrY 8  5
> 4 chr13 9  5.5
> 5  chrX 10 7.5
>
> Yu
>
>
>
>
>
>        [[alternative HTML version deleted]]
>
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

	[[alternative HTML version deleted]]

