[Rd] variance of a scalar (PR#546)

[Jonathan Rougier]

On Fri, 19 May 2000, Prof Brian Ripley wrote:

> > I was surprised to find that the variance of a scalar, using
> > var(), is NA.  Surely this should be zero?
> > 
> 
> Do you mean a vector of length 1? (S has no scalars.)  No, it should be
> NA, as sum((x-xbar)^2)/(n-1) is NaN, or, in statistical terms, one has
> no idea at all of the variability from a single sample.

I thought that might be the reason.  There is no mention of using n-1
rather than n in the denominator on the help page.  Perhaps that might be
added?

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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