On Jan 20, 2010, at 5:37 PM, hongwei wrote:
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.
Please abandon the phrase "doesn't work". Even if modfied by an adverb
it remains basically meaningless.
> merge(x, y, by.x="ToID", by.y="ID")
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
Works fine.
If you want it sorted and arranged the way you specify there are
couple of rearrangements possible:
> merge(x,y,by.x="ToID", by.y="ID")[order(x$ToID),] # re-sorts
ToID FromID X
3 2 1 150
5 3 1 130
1 1 2 100
6 3 2 130
2 1 3 100
4 2 3 150
> merge(x,y,by.x="ToID", by.y="ID")[order(x$ToID), c(2,1,3)] # swaps
col1 and col2
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
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
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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