[Rd] Modification to cov and cor

Jonathan Rougier J.C.Rougier@durham.ac.uk
Fri, 10 Nov 2000 15:59:40 +0000 (GMT)


On 10 Nov 2000, Peter Dalgaard BSA wrote:

> 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.  

I agree with that.  I was thinking that a warning would be
helpful.  Perhaps something along the lines of

if (any(sapply(x, is.factor))) warning("Coercing factor to numeric")

J.

Jonathan Rougier                       Science Laboratories
Department of Mathematical Sciences    South Road
University of Durham                   Durham DH1 3LE
http://www.maths.dur.ac.uk/stats/people/jcr/jcr.html


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