> -----Original Message-----
> From: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] On Behalf Of hongwei
> Sent: Wednesday, January 20, 2010 2:38 PM
> To: r-help@r-project.org
> Subject: [R] Question about many-to-one merge
>
>
> I have spent a whole afternoon searching for the solution,
> but got nothing so
> far. It should be a simple problem.
> I have two datasets to merge. The first one just contains two
> ID columns and
> it looks like:
>
> FromID ToID
> 1 2
> 1 3
> 2 1
> 2 3
> 3 1
> 3 2
>
> The second one contains a ID column and a variable:
> ID X
> 1 100
> 2 150
> 3 130
>
> What I want is to merge the two datasets together using the
> ToID and ID. The
> final merged dataset should look like:
>
> FromID ToID X
> 1 2 150
> 1 3 130
> 2 1 100
> 2 3 130
> 3 1 100
> 3 2 150
>
> The Merge command doesn't work well.
It always helps to see what you did and to
know what you consider "working well". Does
the following do what you want?
> xy <- merge(x,y,by.x="ToID",by.y="ID")
> xy
ToID FromID X
1 1 2 100
2 1 3 100
3 2 1 150
4 2 3 150
5 3 1 130
6 3 2 130
The numbers are all there, but if you want the
rows and columns ordered the way you showed them
then use subscripting to reorder them:
> xy[order(xy$FromID),c("FromID", "ToID", "X")]
FromID ToID X
3 1 2 150
5 1 3 130
1 2 1 100
6 2 3 130
2 3 1 100
4 3 2 150
Use 'rownames(xy)<-...' if you want new row names.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> I also don't want to use
> for loop. I
> feel that there must be some subscripting or other tricks to
> use, but I
> couldn't figure it out.
>
> Any help is appreciated!!
>
> -Hongwei
>
> --
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>
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