[Rd] Modification to cov and cor
Peter Dalgaard BSA
p.dalgaard@biostat.ku.dk
10 Nov 2000 16:52:40 +0100
Jonathan Rougier <J.C.Rougier@durham.ac.uk> writes:
> Can I suggest that in cov and cor the lines
>
> if (is.data.frame(x))
> x <- as.matrix(x)
> if (is.data.frame(y))
> y <- as.matrix(y)
>
> be replaced by
>
> if (is.data.frame(x))
> x <- data.matrix(x) # coerce logical and factors
> if (is.data.frame(y))
> y <- data.matrix(y) # likewise
I'd oppose that, especially for factors. Correlations between factors
are as likely to be nonsens as remotely meaningful.
With the current definition of data.matrix (using codes(f)), even more so:
> data.matrix(data.frame(a=1:3,b=factor(c("mild","medium","severe"))))
a b
1 1 2
2 2 1
3 3 3
!!
--
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
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