[R] R: possibility for sth. like parameter passing by reference?

[Peter Dalgaard BSA]

Thomas Lumley <thomas at biostat.washington.edu> writes:

> On Tue, 1 Feb 2000, Marcus Eger wrote:
> 
> > Hello,
> > is there a possibility to pass parameters to a
> > function without copying them into the new environment?
...
> For example, if I define x to be a really big matrix and then
> R>  g<-function(x) mean(x)+1
> R> f<-function(x) mean(x+1)
> R> g(w)
> [1] 0.9992614
> R> f(w)
> Error: heap memory (6144 Kb) exhausted [needed 1562 Kb more]
> 
> The first function doesn't copy x, the second does.

Interesting... I would have expected that both functions would copy x
when the argument is evaluated, but the 2nd one create an additional
object the same size as x to hold the intermediate value of x+1.

I thought that the copying would be avoided altogether by using

h<-function(x)eval.parent(substitute(mean(x)+1))

but that seems to take as much space as g(), which seems to indicate
that the object is linked rather than copied in such cases.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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