matrix coercion, logical -> character
Prof Brian Ripley <ripley@stats.ox.ac.uk> writes:
On 8 Dec 2003, Peter Dalgaard wrote:
Anyone know whether this is intentional, and by which rationale? (R-devel on RedHat, but hardly new)
It is documented:
'as.matrix' is a generic function. The method for data frames will
convert any non-numeric column into a character vector using
'format' and so return a character matrix.
and for apply:
If 'X' is not an array but has a dimension attribute, 'apply'
attempts to coerce it to an array via 'as.matrix' if it is
two-dimensional (e.g., data frames) or via 'as.array'.
explains why apply(...., which) got in trouble
Remember than not some long ago you could not have logical columns in data frames: they were coerced to factors. It would be easy to change to allow numeric, logical or character matrices.
Yes. That was the direction in which I was hinting. It does seem a bit like a leftover, and applying which() over a set of logical columns is not unlikely to be useful in practice.
O__ ---- Peter Dalgaard Blegdamsvej 3 c/ /'_ --- Dept. of Biostatistics 2200 Cph. N (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk) FAX: (+45) 35327907