[R] building a data.frame from a matrix: preventing conversion to factors

[Prof Brian Ripley]

I am trying to build a data.frame from some vectors and some matrices
and seem to be unable to find out how to do this without converting
everything to factors.
I can prevent conversion of the vectors by using I(), as explained in
help(data.frame). However, this doesn't help with the matrices: if I try
I() with the matrix, the matrix gets incorporated into the data frame as
a whole, rather than as a list of vectors as it should be. ("as.is=T"
doesn't help either, and neither does "options(stringsAsFactors = 
FALSE)".)

I think we need the reproducible example we asked for.  I get

> z <- matrix(letters[1:12], 4, 3)
> z2 <- data.frame(x=1:4, z=z, stringsAsFactors=FALSE)
> sapply(z2, class)
           x         z.1         z.2         z.3
   "integer" "character" "character" "character"

so it is working as documented.  (BTW, using I() on a matrix is intended 
to insert a matrix as a single entity, and as.is is not an argument to 
data.frame.)

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595