# [R] Create a data frame of all possible unique combinations of factors

jim holtman jholtman at gmail.com
Wed Jul 6 02:08:24 CEST 2011

```Missed that you wanted to elim duplicated:

> z <- expand.grid(test,test)
> z\$key <- apply(z, 1, function(x)paste(sort(x), collapse=''))
> str(z)
'data.frame':   16 obs. of  3 variables:
\$ Var1: Factor w/ 4 levels "A","B","C","D": 1 2 3 4 1 2 3 4 1 2 ...
\$ Var2: Factor w/ 4 levels "A","B","C","D": 1 1 1 1 2 2 2 2 3 3 ...
\$ key : chr  "AA" "AB" "AC" "AD" ...
- attr(*, "out.attrs")=List of 2
..\$ dim     : int  4 4
..\$ dimnames:List of 2
.. ..\$ Var1: chr  "Var1=A" "Var1=B" "Var1=C" "Var1=D"
.. ..\$ Var2: chr  "Var2=A" "Var2=B" "Var2=C" "Var2=D"
> subset(z, !duplicated(z\$key))
Var1 Var2 key
1     A    A  AA
2     B    A  AB
3     C    A  AC
6     B    B  BB
7     C    B  BC
8     D    B  BD
11    C    C  CC
12    D    C  CD
16    D    D  DD
>

On Tue, Jul 5, 2011 at 7:16 PM, Q <quagaars at gmail.com> wrote:
> Hello,
>
> I'm trying to create a data frame where each row has a unique combination of
> factors.
>
>
>
>
>> 1> test <- c("A","B","C","D")
>>
>
>> 1> test
>>
>
>> [1] "A" "B" "C" "D"
>>
>
> To get all species combinations I have used expand.grid like this:
>
>
>
>> 1> pairs <- expand.grid(test,test)
>
>> 1> pairs
>
>>    Var1 Var2
>
>> 1     A    A
>
>> 2     B    A
>
>> 3     C    A
>
>> 4     D    A
>
>> 5     A    B
>
>> 6     B    B
>
>> 7     C    B
>
>> 8     D    B
>
>> 9     A    C
>
>> 10    B    C
>
>> 11    C    C
>
>> 12    D    C
>
>> 13    A    D
>
>> 14    B    D
>
>> 15    C    D
>
>> 16    D    D
>>
>
> Now I want to select only the unique pairs, which I have tried to do with
> the function "unique":
>
>
>
>> 1> unique(pairs)
>>
>
> , but that doesn't do anything... I guess because it considers A,B to be
> different from B,A.  The data frame I would like to end up with should look
> like this.
>
>
>
>>    Var1 Var2
>
>> 1     A    A
>
>> 2     B    A
>
>> 3     C    A
>
>> 4     D    A
>
>> 6     B    B
>
>> 7     C    B
>
>> 8     D    B
>
>> 11    C    C
>
>> 12    D    C
>
>> 16    D    D
>
>>
>
>
> Q
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Create-a-data-frame-of-all-possible-unique-combinations-of-factors-tp3647338p3647338.html
> Sent from the R help mailing list archive at Nabble.com.
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>

--
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?

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