[R] data.frame merge matching several columns
Patrick E. McKnight
pem at theriver.com
Tue Oct 8 21:57:49 CEST 2002
Tony,
Right you are! Apologies for overlooking such an obvious feature. Thanks
for your help.
Cheers,
Patrick
> It looks like it works right out of the box. (The documentation for
> merge() in R1.5.1 pretty clearly mentions the possibility of merging on
> multiple columns .)
>
> > m1 <- read.table("tmp1.txt", header=T, row.names=NULL)
> > m2 <- read.table("tmp2.txt", header=T, row.names=NULL)
> > m1
> SUBID TARGID ITEM RATING
> 1 1 1 1 4
> 2 1 1 2 5
> 3 1 1 3 3
> 4 1 1 4 2
> 5 1 1 5 5
> > m2
> TARGID ITEM TARGET
> 1 1 1 5
> 2 1 2 4
> 3 1 3 6
> 4 1 4 2
> 5 1 5 3
> > merge(m1, m2)
> TARGID ITEM SUBID RATING TARGET
> 1 1 1 1 4 5
> 2 1 2 1 5 4
> 3 1 3 1 3 6
> 4 1 4 1 2 2
> 5 1 5 1 5 3
> >
>
> At 11:17 AM 10/8/2002 -0700, you wrote:
>>Greetings,
>>
>>Is it possible to match several columns in a merge statement? Here is
>> my problem:
>>
>>data1 looks like this...
>>
>>SUBID TARGID ITEM RATING
>>1 1 1 4
>>1 1 2 5
>>1 1 3 3
>>1 1 4 2
>>1 1 5 5
>>......
>>
>>SUBID is the ID for the raters, TARGID is the ID for the targets being
>> rated, ITEM ranges from 1 to 64 crossed by TARGID (i.e., all targets
>> were rated on 64 items), and RATING is the rating given by SUBID for
>> each TARGID and ITEM.
>>
>>My second dataset looks like this data2:
>>
>>TARGID ITEM TARGET
>>1 1 5
>>1 2 4
>>1 3 6
>>1 4 2
>>1 5 3
>>.......
>>
>>TARGID again is the target's ID, ITEM ranges from 1 to 64, and TARGET
>> is the rating provided by the target.
>>
>>I would like to merge these two data.frames by TARGID and ITEM to yield
>> the following structure:
>>
>>SUBID TARGID ITEM RATING TARGET
>>1 1 1 4 5
>>1 1 2 5 4
>>1 1 3 3 6
>>1 1 4 2 2
>>1 1 5 5 3
>>........
>>
>>I realize that merge appears to be the proper tool but there is no
>> documentation for how to merge by multiple columns. Is this possible?
>>
>>Thanks in advance for any assistance with the problem.
>>
>>
>>--
>>Cheers,
>>
>>Patrick
>>
>>
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--
Cheers,
Patrick
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