On Mon, Aug 9, 2010 at 9:31 PM, Derek Ogle <do...@northland.edu> wrote:
> I am trying to define a general R function that has a function as the output
> that depends on the user's input arguments (this may make more sense by
> looking at the toy example below). My real use for this type of code is to
> allow a user to choose from many parameterizations of the same general model.
>
> My "issue" is that when I compile a package with this type of code in it I
> get a __warning__ that "multiple local function definitions for 'm' with
> different formal arguments." While this is not a "deadly error" I would like
> to avoid the warning if possible. Can someone provide some guidance? Thank
> you in advance for any help you can offer.
>
> For what it is worth ... I am working on a Windows XP machine with R 2.11.1.
>
>
>
>
> ## A function that allows the user to create a new function that depends on
> their
> ## choice in the type argument. As a simple example, if the user chooses
> "one"
> ## then the output function is exponential growth, if the user choses "two"
> then
> ## thhe output function is logistic growth.
>
> mdlChooser <- function(type=c("one","two")) {
> type <- match.arg(type)
> switch(type,
> one={ m <- function(x,N0,r) N0*exp(x*r) },
> two={ m <- function(x,N0,r,K) (N0*K)/(N0+(K-N0)*exp(-x*r)) },
> )
> m
> }
>
> ## define time steps
> t <- 0:10
>
> ## create a function -- junk1 -- that produces exponential growth
> junk1 <- mdlChooser("one")
> junk1
> res1 <- junk1(t,500,0.2)
> res1
>
> ## create a function -- junk2 -- that produces logistic growth
> junk2 <- mdlChooser("two")
> junk2
> res2 <- junk2(t,500,0.2,1000)
> res2
>
Try this:
mdlChooser <- function(type = c("one", "two")) {
one <- function(x,N0,r) N0*exp(x*r)
two <- function(x,N0,r,K) (N0*K)/(N0+(K-N0)*exp(-x*r))
type <- match.arg(type)
get(type)
}
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