Hi Udo,

Perhaps

> merge(treat,control)

does what you need.

I hope this helps,

Jorge


On Sun, Apr 13, 2008 at 2:41 PM, Udo <ukoenig@med.uni-marburg.de> wrote:

> Hi,
> I have a frame "treat" and want to find matched pairs in the data frame
> "control". In the matched (combined) data frame there should be two
> variables (0/1),indicating the "source" of the data (treat or control),
> so that it is possibe to set a "filter" (extraxt/select data).
>
> #Here are the dataframes (my real data frames have many variables)
> treat <- data.frame(age=c(1,1,2,2,2,4),
>                    school=c(10,10,20,20,20,11),
>                    out1=c(9.5,2.3,3.3,4.1,5.9,4.6))
> control <- data.frame(age=c(1,1,1,1,3,2),
>                      school=c(10,10,10,10,33,20),
>                      out2=c(1.1,2,3.5,4.9,5.2,6.5))
> print(treat)
> print(control)
>
> matched.data.frame <- ?????? #Match "treat" "control" by age school
>
>
> #My SPSS syntax would be similar to this:
> MATCH FILES FILE="treat" /IN=fromtreat
>  /FILE="control" /IN=fromcontrol
>  /BY age school.
> SELECT IF fromdad AND fromfam. #select data, set filter
>
> The /IN= option creates a 0/1 variable that indicates the
> "source" of the data
>
> The resultand matched data frame should have
> the following structure:
> age   school    out1    out2  fromtreat     fromcontrol
> 1       10      9.5     1.1     1               1
> 1       10      2.3     2.0     1               1
> ....
> 4       11      4.6     NA      1               0
> 3       33      NA      5.2     0               1
> ....
>
> I tried "which" and "match", but I failed and was unlucky looking
> at the help/archive. Merge doesn´t do the job, because it makes
> all possible matches.
>
>
> Thank´s for any help!
> Udo
>
>
> --------------------------------------------
> Udo K    N     G
>      Ö     I
>
> Clinic for Child an Adolescent Psychiatry
> Philipps University of Marburg / Germany
>
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