Maintaining factors when copying from one data frame to another

Greetings all:

OK, this is bugging the @#@%* out of me. I know the answer is simple
and straightforward but for the life of me I cannot find it in the
documentation, in the archives, or in my notes (because I know I've
encountered this in the past). My problem is:

I have a data frame with columns A, B, C, D, and E. A, B, and E are
factors and C and D are numeric. I need a new data frame with just A,
C, and D. When I copy these columns to a new data frame

 

newDF <- data.frame(cbind(oldDF$A, oldDF$C, oldDF$D))
   

all the factor data comes out as levels rather than the original
factors. How do I preserve the factors when I copy from one data frame
to another?


Thanks vary much,
Kurt Wollenberg, Ph.D.
Tufts Center for Vision Research
Tufts-New England Medical Center
750 Washington St #450
Boston, MA 02111
Office: 617-636-9028
Fax: 617-636-8945
email: kurt.wollenberg at gmail dot com