R help - Jun 2006 - Compact sums in functions definitions

I'm trying to make more compact the definition
of a function as for example:

f <- function(x) 2/x+3/x

by simply defining the array of coefficients

arr = c(2,3)

and setting:

g <- function(x) sum((arr/x))

Everything seems to work fine because the values returned 
by f and g result coincident for different values of their
argument, but when I try to plot the function g using:

x = seq(-1,1,.01)
plot(x,g(x))

I receive the errors/warnings:
>Error in xy.coords(x, y, xlabel, ylabel, log) : 
>        'x' and 'y' lengths differ
>In addition: Warning message:
>longer object length
>        is not a multiple of shorter object length in: b/t 
>Execution halted
Any idea about that?

Thanks.

Alessandro

-- 
===========================================================Alessandro Antonucci
Dalle Molle Institute for Artificial Intelligence (IDSIA)
at Idsia			e-mail: alessandro at idsia.ch
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Switzerland			skype: alessandro.antonucci

Hi Alessandro,

The problem is that arr/x isn't quite doing what you
thought it was.
arr / x is something like
c(arr[1] / x[1], arr[2] / x[2], arr[1] / x[3], ...)
What I mean is, it divides arr[i] by x[i] and tries to lengthen
arr by repeating itself (because it is shorter than x). It warns
in case length(x) is not a multiple of length(arr).
(or the other way around if arr was longer than x)

I made a nice one for you:
g <- function(x) rowSums( t(t(1/x)) %*% arr )

It is likely someone else can do it much nicer (shorter),
my R knowledge still has to be increased ...

JeeBee.


On Thu, 15 Jun 2006 18:55:15 +0200, Alessandro Antonucci wrote:
> I'm trying to make more compact the definition
> of a function as for example:
> 
> f <- function(x) 2/x+3/x
> 
> by simply defining the array of coefficients
> 
> arr = c(2,3)
> 
> and setting:
> 
> g <- function(x) sum((arr/x))
> 
> Everything seems to work fine because the values returned 
> by f and g result coincident for different values of their
> argument, but when I try to plot the function g using:
> 
> x = seq(-1,1,.01)
> plot(x,g(x))
> 
> I receive the errors/warnings:
> 
>>Error in xy.coords(x, y, xlabel, ylabel, log) : 
>>        'x' and 'y' lengths differ
>>In addition: Warning message:
>>longer object length
>>        is not a multiple of shorter object length in: b/t 
>>Execution halted
> 
> Any idea about that?
> 
> Thanks.
> 
> Alessandro