# Re: [R] intersecting rows of a matrix

From: dxc13 <dxc13_at_health.state.ny.us>
Date: Wed, 20 Feb 2008 17:50:08 -0800 (PST)

Thank you, that also works perfectly! I am not sure which method works more efficiently, but they are both instantaneous and give the correct result. Thanks

Derek

Henrique Dallazuanna wrote:

```>
> lk.list<-split(lk.mat.test,1:nrow(lk.mat.test))
> names(lk.list)<-NULL
> do.call(intersection,lk.list)
>
> 2008/2/20, dxc13 <dxc13_at_health.state.ny.us>:
```

>>
>> useR's,
>>
>> First, I would like to say thanks to John Fox for providing this segment
>> of
>> code to perform intersection for multiple sets:
>> intersection <- function(x, y, ...){
>> if (missing(...)) intersect(x, y)
>> else intersect(x, intersection(y, ...))
>> }
>>
>> I want to execute this function on the rows of a matrix I have:
>> Ik.mat.test <- matrix(c(2,3,6,1,2,6,6,1,2),byrow=T,nrow=3)
>> > Ik.mat.test
>> [,1] [,2] [,3]
>> [1,] 2 3 6
>> [2,] 1 2 6
>> [3,] 6 1 2
>>
>> I need to find a way to run the intersection function on the rows of this
>> matrix. The result should be a vector containing 2, 6.
>> This works, but I want to find a way to do this for any size matrix.
>> intersection(Ik.mat.test[1,],Ik.mat.test[2,], Ik.mat.test[3,])
>> So, if the user supplied a matrix with any number of rows, I would like
>> to
>> be able to run this function. Any ideas?
>> I have tried something like
>> do.call(intersection, list(Ik.mat.test[1,]: Ik.mat.test[3,]))
>> but this doesnt work
>>
>> Derek
>>
>>
>>
>> --
>> View this message in context:
>> http://www.nabble.com/intersecting-rows-of-a-matrix-tp15601658p15601658.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
>> ______________________________________________
>> R-help_at_r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
```>
>
> --
> Henrique Dallazuanna
> Curitiba-Paraná-Brasil
> 25° 25' 40" S 49° 16' 22" O
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>

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