Hi all
I have a question about "subset" function.
> dat
id x1 x2 x3
1 a 1 11 111
2 b 2 22 222
3 c 3 33 333
4 d 4 44 444
> subset(dat,id==c("a","c"))
id x1 x2 x3
1 a 1 11 111
> subset(dat,id==c("a","d"))
id x1 x2 x3
1 a 1 11 111
4 d 4 44 444
>From the above, if I choose id=a,c, the result is wrong,but if I choose
>id=a,d, the result is right.
What's the reason for it?
Many thanks!
My best
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