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

Prof Brian Ripley Prof Brian Ripley <ripley@stats.ox.ac.uk>
Fri, 19 May 2000 09:48:53 +0100 (BST)

> From: J.C.Rougier@durham.ac.uk
> Date: Fri, 19 May 2000 10:42:04 +0200 (MET DST)
> 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.

S gives NA too.

Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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