[R] matching matrix columns to a vector

[David Winsemius]

Since negative values could balance positives, you might need to use:
which(colSums(abs(t-v)) == 0)

 > t=matrix(1:12,3,4)
 > v=c(1,2,3)
 > which(colSums(t-v) == 0)
[1] 1
 > t
      [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12
 > t[1,2] <- -5
 > which(colSums(t-v) == 0)
[1] 1 2

 > which(colSums(abs(t-v)) == 0)
[1] 1


--  
David Winsemius
Heritage Labs

On Nov 24, 2008, at 11:59 AM, <Jagat.K.Sheth at wellsfargo.com> <Jagat.K.Sheth at wellsfargo.com 
 > wrote:

> How about which(colSums(t-v) == 0) ?
>
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org 
> ]
> On Behalf Of Salas, Andria Kay
> Sent: Monday, November 24, 2008 10:04 AM
> To: r-help at r-project.org
> Subject: [R] matching matrix columns to a vector
>
> I need help with (hopefully) just one more thing.  I have been fussing
> with this for quite some time and have decided just to give up and  
> ask!
> I want to match a column in a matrix to a vector.  I found a "which"
> command that I thought would be helpful as it does the following:
>
>> g=c(1,5,3,2,7)
>> which(g==5)
> [1] 2
>
> As the above gave which placement in the g vector corresponded to 5  
> (the
> second place), I need this command to give me which column in a matrix
> matches to a vector.
>
> This is just a toy example of what I am trying to do:
>> t=matrix(1:12,3,4)
>> v=c(1,2,3)
>> which(t[,j]==v)
>
> This does not work, and with my "real" matrices and vectors, I was
> getting outputs that did not make sense.  These examples are more to
> give an idea of what I am aiming to accomplish.
>
> Thank you for all the help!!
> ______________________________________________
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>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.