Re: [R] pass functions and arguments to function

Duncan Murdoch Tue, 29 Dec 2009 14:55:08 -0800

On 29/12/2009 5:24 PM, Hao Cen wrote:

Thanks. I don't know how many functions there will be.


What if g1, g2, g3 have variable number of parameters? say g1 has parg1a,
parg1b, and g3 has parg3a, parg3b, parg3c, parg4d.

pars could be a list of lists of parameters instead of a list ofparameters, then the calls could be


do.call(fs[[i]], pars[[i]])

But it's very unlikely that you are doing something that's a good idea.

Duncan Murdoch


 f <- function(X, fs, pars) {
    process1(X)
    for (i in 1:length(fs))
      fs[[i]](pars[[i]])   # doesn't work here

    process2(X)

 }


On Tue, December 29, 2009 4:57 pm, Duncan Murdoch wrote:

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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