Thanks！






在 2012-01-13 10:51:14，"Jorge I Velez" <jorgeivanvelez@gmail.com> 写道：
Hi,


Use %in% instead of ==.


HTH,
Jorge.-



On Thu, Jan 12, 2012 at 9:36 PM, 孟欣 <> wrote:
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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