Hello,

I'm clearly confused about the merge function. In the following

r <- merge(x,y,all.x=T,all.y=F)

my y vector has only unique values (no duplicates). So I don't understand
how this can ever generate an r which is of greater length than x. 

I thought the default behavior was only matching rows are included, but
that using all.x=T included rows with unmatched x's as well. If all the y's
are unique, though, I don't understand how length(r) > length(x) is
possible. 

Some clarification would be great.

Thanks,
Mitch


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