[R] Indexing column of a matrix with infix $

[chris1]

I'm using 1.9.0 on Windoze 2k and I created a numeric matrix and used
colnames() to give it some column names, but if I try to select a
column using matrixname$validname I get a null return but if I use
matrixname[,4] it works fine.  Looking at the help I think this is
because a matrix is not a recursive structure and I think it's saying
I shouldn't be surprised nor attempt this.

I'm in the process of transferring all my stats work to R having used
a mixture of SPSS, S and SAS (and snippets of other things) over the
years so sorry if I'm being dumb but this surprised me and I'd love a
kindly explanation as I thought indexing a matrix in this way was
something I did regularly (I think the last time was actually using it
on a dataframe though) and I also think it would be useful and produce
more readable code if I could.

Can some kindly soul explain?

TIA,

Chris