[R] Merge problem

From: Tova Fuller <suprtova_at_ucla.edu>
Date: Fri 22 Sep 2006 - 09:09:26 GMT

Hello all,

I have read as many merge issues as I possibly could tonight and although I presume this is a small error, I have not found the solution to my problem.

I'm trying to merge two data sets: dat0 and TransTable. As you can see below, dat0 has 8000 rows, whereas TransTable has 47296 rows. I would expect when I merge the two data sets, with all.x=F, and all.y=F, that the intersection would yield 8000 rows, considering dat0 is a subset of TransTable.

However, I get a neat little surprise when I check the dimensions of the resultant data frame - dat0merge, the merged data frame has 8007 rows! How can this be? Where did these extra 7 rows come from? This appears to defy logic!

Thank you in advance for your help. I've put my code below for reference.

Tova Fuller

> dim(dat0)

[1] 8000 60
> dim(TransTable)

[1] 47296 9
> dat0merge=merge(TransTable,dat0,


> dim(dat0merge)

[1] 8007 68

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