[R] outer

Prof Brian Ripley ripley at stats.ox.ac.uk
Sun Sep 23 17:14:04 CEST 2001

On Sun, 23 Sep 2001, Erich Neuwirth wrote:

> i cannot cajole outer in doing what i want it to do.
> i hav a function only defined for scalars
> fun(n,k)
> and i want to do
> outer(1:5,1:5,function(x,y) fun(x,y))
> (i know this is written somewhat clumsy)
> to get an array with the values of fun
> to use it as an input for image
> this does not work since
> outer assumes then fun works on arrays elementwise.
> what is the easiest way of getting what i want?
> outer in some lisp like variants and in mathematica will work with the
> function argument being a
> scalar argument only function.
> r is different here.

Well, R is a vector language and expect functions to handle vector
arguments.  In fact it has no scalars, so I guess you mean that it will
only accept vectors of length one.  You'll need to use loops, implicitly
(via *apply) or explicitly.  Probably best to do this inside f, and make
it conform to the R model.

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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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