[R] Power functions?

[Prof Brian Ripley]

Please post to only one of

r-help at r-project.org
r-help at stat.math.ethz.ch

not to both, as the same list then got two copies.

On Sat, 3 Jan 2009, rkevinburton at charter.net wrote:

> I had a question about the basic power functions in R.
>
> For example from the R console I enter:
>
> -1 ^ 2
> [1] -1
>
> but also
>
> -1^3
> [1] -1
>
> -0.1^2
> [1]  -0.01
>
> Normally pow(-1, 2) return either -Infinity or NaN. Has R taken over
> the math functions? If so I would think that -1^2 is 1 not -1 and -0.1^2 
> is 0.01 not -0.01.

See ?Syntax, linked from ?`^` :

      The following unary and binary operators are defined.  They are
      listed in precedence groups, from highest to lowest.

        '[ [['             indexing
        ':: :::'           access variables in a name space
        '$ @'              component / slot extraction
        '^'                exponentiation (right to left)
        '- +'              unary minus and plus

so -1^2 is -(1^2) not (-1)^2.

-- 
Brian D. Ripley,                  ripley at 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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595