[R] define subgroups based on position in table

[jim holtman]

try this:

> x <- read.table(textConnection("group
+ A
+ A
+ A
+ B
+ B
+ A
+ A
+ B
+ B
+ B
+ A
+ A"),header=TRUE, as.is=TRUE)
> closeAllConnections()
> # use rle to get the 'runs'
> x.rle <- rle(x$group)
> # now generate the group numbers
> x.grp <- ave(x.rle$values, x.rle$values, FUN=seq_along)
> # put the numbers back
> x$sub <- with(x.rle, paste(rep(values, lengths), rep(x.grp, lengths), sep=''))
>
>
> x
   group sub
1      A  A1
2      A  A1
3      A  A1
4      B  B1
5      B  B1
6      A  A2
7      A  A2
8      B  B2
9      B  B2
10     B  B2
11     A  A3
12     A  A3
>


On Tue, Jul 20, 2010 at 8:02 AM, STEVENS, Maarten
<Maarten.STEVENS at inbo.be> wrote:
> Dear list,
>
> I have a data frame with one column (group) and want to add a second column (sub) with a serial number that says to which subgroup a cell belongs. A subgroup contains the consecutive rows of the same group. The number of a subgroup is based on its position in the table. The first subgroup of A's and B's should have nr A1 and B1, the second nr A2 and B2, etc.. I hope the example below makes things more clear.
> This is what my data look like:
>
> x <- read.table(textConnection("group
> A
> A
> A
> B
> B
> A
> A
> B
> B
> B
> A
> A"),header=TRUE)
> closeAllConnections()
>
>   group
> 1      A
> 2      A
> 3      A
> 4      B
> 5      B
> 6      A
> 7      A
> 8      B
> 9      B
> 10     B
> 11     A
> 12     A
>
> This is what it should become:
>
>   group sub
> 1      A A1
> 2      A A1
> 3      A A1
> 4      B B1
> 5      B B1
> 6      A A2
> 7      A A2
> 8      B B2
> 9      B B2
> 10     B B2
> 11     A A3
> 12     A A3
>
>
>
>
>
> Maarten Stevens
>
> Senior onderzoeker - Aquatisch Beheer / Senior scientist - Aquatic Management
>
>
>
> INBO – Instituut voor Natuur- en Bosonderzoek / Research Institute for Nature and Forest
>
> Afdeling Beheer en Duurzaam Gebruik / Dept. Management and Sustainable Use
>
> Kliniekstraat 25 Ÿ B-1070 Brussels, BELGIUM
>
> E-mail: maarten.stevens at inbo.be <mailto:maarten.stevens at inbo.be>
>
> Phone: +32.2.558.19.18 Ÿ Gsm / Cell: +32.492.72.28.97 Ÿ Fax: +32.2.558.18.05 Ÿ www.inbo.be <http://www.inbo.be/>
>
>
>
>
>
>
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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