It would be safer to substitute "all.equal(x,v) == TRUE" for every instance where "identical(x,v)" appears below.

Identical does not behave as I believed it did, and all.equal needs to be tested in order to to properly handle situations in which it returns a character value.

> apply(t,2,function(x) all.equal(x,v))
[1] "TRUE" "Mean relative difference: 0.6" [3] "Mean relative difference: 0.75" "Mean relative difference: 0.8181818"
> which(apply(t,2,function(x)all.equal(x,v)))
Error in which(apply(t, 2, function(x) all.equal(x, v))) :
  argument to 'which' is not logical


> apply(t,2,function(x) all.equal(x,v) == TRUE)
[1]  TRUE FALSE FALSE FALSE
> which(apply(t,2,function(x) all.equal(x,v) == TRUE))
[1] 1

--
David Winsemius

On Nov 24, 2008, at 1:02 PM, David Winsemius wrote:

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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