I have found something that partially works. Just to illustrate what am
I looking for:

for(a in colnames(ar1)) {if(a %in% colnames(ar2)) { cat(a, "\t",
ar1[,a],"\t",ar2[,a],"\n")}}
A        1 2 3 4         5 6 7 8
B        5 6 7 8         13 14 15 16
E        13 14 15 16     9 10 11 12

I think I can use something similar to obtain the desired results, but I
am curious to know if there is a better way to do it.
Federico


Federico Abascal wrote:
> Dear all,
>
> I have a problem that may be someone of you can help. I am a newbie and
> do not find how to do it in manuals.
>
> I have two arrays, for example:
>
> ar1 <- array(data=c(1:16),dim=c(4,4))
> ar2 <- array(data=c(1:16),dim=c(4,4))
> colnames(ar1)<-c("A","B","D","E")
> colnames(ar2)<-c("C","A","E","B")
>
>   
>> ar1
>>     
>      A B  D  E
> [1,] 1 5  9 13
> [2,] 2 6 10 14
> [3,] 3 7 11 15
> [4,] 4 8 12 16
>   
>> ar2
>>     
>      C A  E  B
> [1,] 1 5  9 13
> [2,] 2 6 10 14
> [3,] 3 7 11 15
> [4,] 4 8 12 16
>
>
> I would like to join both arrays only for the columns present in both
> ar1 and ar2 (the intersection). I would like to obtain this:
>      A B  E
> [1,] 1 5 13
> [2,] 2 6 14
> [3,] 3 7 15
> [4,] 4 8 16
> [5,] 5 13  9
> [6,] 6 14 10
> [7,] 7 15 11
> [8,] 8 16 12
>
> (rows 5-8 correspond to ar2)
>
> I have tried several things but I am unable to accomplish it. Any
> experienced user could give me some advice, please?
>
> I have another question: how can I sort the columns of an array
> according to its column names (for ar2, change CAEB to ABCE)?
>
> Thanks in advance!
> Federico
>
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> and provide commented, minimal, self-contained, reproducible code.
>
>   


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