[R] pass functions and arguments to function

[Duncan Murdoch]

On 29/12/2009 3:08 PM, Hao Cen wrote:
> Hi,
> 
> I wonder how to pass several functions and their arguments as arguments to
> a function. For example, the main function is
> 
> f = function(X  ) {
>    process1(X)
>    ...
> 
> 
>    process2(X)
> }
> 
> I have a few functions that operate on X, e.g. g1(X, par1), g2(X, par2),
> g3(X, par3).  par1, par2 and par3 are parameters and of different types. I
> would like to pass g1, g2, g3 and their arguments to f and g1, g2, g3 may
> appear to be in different orders. So that final effect of the passing is

Just pass them.  If you know there are three functions, set up f as

f <- function(X, f1, f2, f3, par1, par2, par3) {
   process1(X)
   f1(X, par1)
   f2(X, par2)
   f3(X, par3)
   process2(X)
}

and call it as

f(X, g1, g2, g3, par1, par2, par3)

If you don't know how many functions there will be, put them in a list:

f <- function(X, fs, pars) {
   process1(X)
   for (i in 1:length(fs)) fs[[i]](pars[[i]])
   process2(X)
}

and call it as

f(X, list(g1, g2, g3), list(par1, par2, par3))

Duncan Murdoch

> 
> f = function(X  ) {
>    process1(X)
>    g1(X, par1)
>    g2(X, par2)
>    g3(X, par3)
>    process2(X)
> }
> 
> If I pass g2(X, par2),g3(X, par3), g1(X, par1) to f, I would expect to get
> the effect of
> f = function(X  ) {
>    process1(X)
>    g2(X, par2)
>    g3(X, par3)
>    g1(X, par1)
>    process2(X)
> }
> 
> Appreciate any suggestions.
> 
> thanks
> 
> Jeff
> 
> 
> ps please ignore my previous blank subject email. It was accidentally sent
> before the letter was completed.
> 
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