R help - Sep 2001 - outer

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.




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Erich Neuwirth, Computer Supported Didactics Working Group
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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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