[R] matching matrix columns to a vector

[David Winsemius]

Consider:

 > apply(t,2,function(x)identical(x,v))
[1]  TRUE FALSE FALSE FALSE

 > apply(t,2,function(x)identical(x,v))+0
[1] 1 0 0 0

and if you wanted to get the position you could use which:
 > which(apply(t,2,function(x)identical(x,v)))
[1] 1

 > t[,4] <- v
 > which(apply(t,2,function(x)identical(x,v)))
[1] 1 4

--  
David Winsemius
On Nov 24, 2008, at 11:03 AM, Salas, Andria Kay wrote:

> 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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