[R] give all combinations

[Peter Dalgaard]

Lucien Lemmens wrote:
> Yuan Jian <jayuan2008 <at> yahoo.com> writes:
>
>   
>> Hello,
>>  
>> is there a simple way to give all combinations for a given vector:
>>  
>> v<-c("a","b","c")
>>  
>> combination(v,v) becomes
>> "aa","ab","ac","bb","bc","cc'
>>  
>> combination(v,v,v) becomes
>> "aaa","aab","aac","abb",......
>>  
>>     
> vv<-c(outer(v,v,paste))
>  vv
> [1] "a a" "b a" "c a" "a b" "b b" "c b" "a c" "b c" "c c"
> vvv<-c(outer(vv,v,paste)
>  vvv
>  [1] "a a a" "b a a" "c a a" "a b a" "b b a" "c b a" "a c a" "b c a" 
> "c c a" "a a b" "b a b" "c a b" "a b b" "b b b" 
> "c b b"
> [16] "a c b" "b c b" "c c b" "a a c" "b a c" "c a c" 
> "a b c" "b b c" "c b c" "a c c" "b c c" "c c c"
>
>   
Notice that "ca" was not in the request for combination(v,v), so it's a 
bit trickier. I was thinking ?combn, but that doesn't count the 
duplicated cases:

 > combn(v,2)
     [,1] [,2] [,3]
[1,] "a"  "a"  "b"
[2,] "b"  "c"  "c"


-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
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