[R] Cohen's Kappa for beginners

[Jason Priem]

Hi,
I've got two vectors with ratings from two coders, like this:

x<-c("red", "yellow", "blue", "red")  #coder number 1
y<-c("red", "blue", "blue", "red") #coder number 2

I want to find Cohen's Kappa using the wkappa function in the psych 
package.  The only example in the docs is using a matrix, which I'm 
afraid I don't understand--I don't know how to get there from what I've 
got.  Could anyone point me in the right direction?  Thanks!
Best,
Jason

-- 
Jason Priem
UNC Royster Fellow
School of  Information and Library Science
University of North Carolina at Chapel Hill