R help - Apr 2009 - Creating a model.matrix with a logical data matrix

Hi,

I'm trying to create a model.matrix (or use lm, which result in the
same issue), using a logical data matrix.
When I use a numerical matrix, I can do:

numeric_mat<-matrix(c(1,2,3,4),c(2,2))
model.matrix(~numeric_mat)

and it works well.

When I use logical matrix:

logic_mat<-matrix(c(TRUE,FALSE,FALSE,TRUE),c(2,2))

#The following works:
model.matrix(~logic_mat[,1]+logic_mat[,2])
#but this fails:
model.matrix(~logic_mat)

Any hint?

Thanks, Ehud