I think you meant to use Depth as the grouping factor rather than s_name:

> ddply(my_data, .(s_name), function(x){
+         x$Im_looking <- x$Depth + as.numeric(factor(x$s_name)) / 100
+         x
+ })
   Depth s_name index Im_looking
1   3852 Site_1   144    3852.01
2   3852 Site_1   144    3852.01
3   3852 Site_1   144    3852.01
4   3852 site_A   145    3852.01
5   3852 site_A   145    3852.01
6   3852 site_A   145    3852.01
7   3852 site_A   145    3852.01
8   3852 site_B   147    3852.01
9   3852 site_B   147    3852.01
10  3852 site_B   147    3852.01
11  3852 site_B   147    3852.01
12 54962 site_C    27   54962.01
13 54962 site_C    27   54962.01
14 54962 Site_D   217   54962.01
15 54962 Site_D   217   54962.01
16 54962 Site_D   217   54962.01
17 54962 Site_D   217   54962.01
> ddply(my_data, .(Depth), function(x){
+         x$Im_looking <- x$Depth + as.numeric(factor(x$s_name)) / 100
+         x
+ })
   Depth s_name index Im_looking
1   3852 Site_1   144    3852.01
2   3852 Site_1   144    3852.01
3   3852 Site_1   144    3852.01
4   3852 site_A   145    3852.02
5   3852 site_A   145    3852.02
6   3852 site_A   145    3852.02
7   3852 site_A   145    3852.02
8   3852 site_B   147    3852.03
9   3852 site_B   147    3852.03
10  3852 site_B   147    3852.03
11  3852 site_B   147    3852.03
12 54962 site_C    27   54962.01
13 54962 site_C    27   54962.01
14 54962 Site_D   217   54962.02
15 54962 Site_D   217   54962.02
16 54962 Site_D   217   54962.02
17 54962 Site_D   217   54962.02

Dennis

On Mon, Mar 14, 2011 at 10:53 AM, Hadley Wickham <hadley@rice.edu> wrote:

> On Mon, Mar 14, 2011 at 9:59 AM, ONKELINX, Thierry
> <Thierry.ONKELINX@inbo.be> wrote:
> > Something like this?
> >
> > my_data=read.table("clipboard", header=TRUE)
> > my_data$s_name <- factor(my_data$s_name)
> > library(plyr)
> > ddply(my_data, .(s_name), function(x){
> >        x$Im_looking <- x$Depth + as.numeric(x$s_name) / 100
> >        x
> > })
>
>
> I think you need factor in there:
>
> ddply(my_data, .(s_name), function(x){
>         x$Im_looking <- x$Depth + as.numeric(factor(x$s_name)) / 100
>         x
> })
>
> or with transform:
>
> ddply(my_data, "s_name", transform,
>  Im_looking = Depth + as.numeric(factor(s_name)) / 100)
>
> Hadley
>
> --
> Assistant Professor / Dobelman Family Junior Chair
> Department of Statistics / Rice University
> http://had.co.nz/
>
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