[R] help about loop

[David Winsemius]

On Feb 18, 2011, at 11:06 PM, 韩文衡 wrote:

>
> Hi all,
> I am try to do a loop  on a data .such as:
>
>> X<-data.frame(name=c(1:9),SN=c(1,1,1,2,2,2,3,3,3),EW=rep(1:3,3))
>> X
>  name SN EW
> 1    1  1  1
> 2    2  1  2
> 3    3  1  3
> 4    4  2  1
> 5    5  2  2
> 6    6  2  3
> 7    7  3  1
> 8    8  3  2
> 9    9  3  3
>
>
>> out<-list()
>> for ( i in 1:3) {out[[i]]<-subset( X,X$SN==1&EW==i) }  ##this  
>> expression can have the subset of EW=1 (and EW=2 EW=3) when SN=1
>> out
> [[1]]
>  name SN EW
> 1    1  1  1
>
> [[2]]
>  name SN EW
> 2    2  1  2
>
> [[3]]
>  name SN EW
> 3    3  1  3
>
>>
>
> Question:  What can I do if I want to have the all subset at once   
> when SN=1:3 ? How to write the loop?

?split

>
> thank you very much!
>
> ----hanwenheng
>
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David Winsemius, MD
West Hartford, CT