question about mean
Rolf Turner wrote:
On 9/02/2009, at 4:40 PM, Bill.Venables at csiro.au wrote:
Store your 'matrix' as a data frame.
Surely it's a data frame already, since ``school'' is character or
factor,
and ``value'' is (must be?) numeric.
People have this unfortunate predilection to refer to data frames as
matrices, and this messes them, and everybody else, up.
still, a naive user's messing up data frames with matrices seems no worse than an experrienced (?) r programmer's messing up lists with vectors. vQ