R help - May 2011 - Group by multiple variables

Hello,

I would like to create a group variable that is based on the values of three
variables:

For example,
> dat <- data.frame(A=c(1,1,1,1,1,2,2,2,2,2),
                    B=c(1,1,1,5,5,5,9,9,9,9),
                    C=c(1,1,1,1,1,2,2,7,7,7))
> dat
   A B C
 1  1 1 1
 2  1 1 1
 3  1 1 1
 4  1 5 1
 5  1 5 1
 6  2 5 2
 7  2 9 2
 8  2 9 7
 9  2 9 7
10 2 9 7

All rows that that are equal, belong to the same group, that is I would like to
create a group variable like this:

   A B C group
 1  1 1 1   1
 2  1 1 1   1
 3  1 1 1   1
 4  1 5 1   2
 5  1 5 1   2
 6  2 5 2   3
 7  2 9 2   4
 8  2 9 7   5
 9  2 9 7   5
10 2 9 7   5

Is there an easy way to do this? Right now I use a bunch of loops and that seems
rather cumbersome. In general, my data set is rather large and the number of
categories per variable is not always fixed.

Franco

Hi,

There are probably much better ways, but try this

transform(dat, group = as.numeric(factor(paste(A,B,C, sep=""))))

HTH,

baptiste

On 31 May 2011 09:47, Mendolia, Franco <fmendolia at mcw.edu>
wrote:
> Hello,
>
> I would like to create a group variable that is based on the values of
three variables:
>
> For example,
>
>> dat <- data.frame(A=c(1,1,1,1,1,2,2,2,2,2),
> ? ? ? ? ? ? ? ? ? ?B=c(1,1,1,5,5,5,9,9,9,9),
> ? ? ? ? ? ? ? ? ? ?C=c(1,1,1,1,1,2,2,7,7,7))
>> dat
> ? A B C
> ?1 ?1 1 1
> ?2 ?1 1 1
> ?3 ?1 1 1
> ?4 ?1 5 1
> ?5 ?1 5 1
> ?6 ?2 5 2
> ?7 ?2 9 2
> ?8 ?2 9 7
> ?9 ?2 9 7
> 10 2 9 7
>
> All rows that that are equal, belong to the same group, that is I would
like to create a group variable like this:
>
> ? A B C group
> ?1 ?1 1 1 ? 1
> ?2 ?1 1 1 ? 1
> ?3 ?1 1 1 ? 1
> ?4 ?1 5 1 ? 2
> ?5 ?1 5 1 ? 2
> ?6 ?2 5 2 ? 3
> ?7 ?2 9 2 ? 4
> ?8 ?2 9 7 ? 5
> ?9 ?2 9 7 ? 5
> 10 2 9 7 ? 5
>
> Is there an easy way to do this? Right now I use a bunch of loops and that
seems rather cumbersome. In general, my data set is rather large and the number
of categories per variable is not always fixed.
>
> Franco
> ______________________________________________
> R-help at 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.
>

On Mon, 30 May 2011 16:47:45 -0500,
"Mendolia, Franco" <fmendolia at mcw.edu> wrote:
> Hello, I would like to create a group variable that is based on the
> values of three variables:
> For example,
>> dat <- data.frame(A=c(1,1,1,1,1,2,2,2,2,2),
>                     B=c(1,1,1,5,5,5,9,9,9,9),
> C=c(1,1,1,1,1,2,2,7,7,7))
>> dat
>    A B C 1 1 1 1 2 1 1 1 3 1 1 1 4 1 5 1 5 1 5 1 6 2 5 2 7 2 9 2 8 2 9
> 7 9 2 9 7 10 2 9 7
[...]

One option:

dat <- within(dat, {grp <- factor(paste(A, B, C))})


-- 
Seb