[BioC] Classification and the Golub data set

[Chelsea Ellis]

Hi,

I'm just learning Bioconductor, and I'm trying to do KNN classification 
using the Golub test and training sets with ALL and AML as the classifier.

When I use the function

knn(golubTrain, golubTest, cl=golubTrain$ALL.AML, k=3),

it's says that the lengths of the training set and the classifier don't 
match.  The documentation on KNN says you need to have the test and training 
sets in matrix form, but I'm not sure how to change an expression set into a 
matrix.  I tried "unclass" and "as.matrix" with no luck.  This is probably 
an easy question, but I'm stuck.  Thanks for any help you can give.

Chelsea