R help - Aug 2011 - Passing a large amount of parameters to a function

Hello,

I have a function with a long list of parameters (of different types,
numeric and string)

myFunc <-function(p1, p2, p3, p4, p5...etc)
{
   do.something(p1,p2,....)
}

I want to loop over this to provide a different set of parameters to the
list every time.

for (ii in 1:N)
{
   myFunc(p1(ii), p2(ii),....etc)
}

I would like to simplify the notation and use some kind of structure, maybe
a list or dataframe.
However when I try, for example, the following:

params = data.frame(cbind(p1=c(1,2,3), p2=5, p3=c(3,2,1)))
myFunc <-function(params)
{
   attach(params)
   do.something(p1,p2,....)
   detach(params)
}
for (ii in 1:N)
{
   myFunc(params[ii,])
}


do.something fails because p1, p2,... are now factors, and i have to
as.numeric() or as.char() each parameter before applying mathematical
operators (such as simple multiplication).
This defeats the purpose of simplifying the code.

Is there any decent, simple way of doing this?
Can I unfactor a row of a data.frame? or a list?
(BTW, "as.numeric()" won't work since some of the parameters are
strings,
same goes for stringsAsFactors in data.frame)

Thanks,
Eran

	[[alternative HTML version deleted]]

You could use something like the following:

paramsList <- list(p1 = 1:10, p2 = -5:5, p3 = 5, p4 = 8)
params <- unlist(as.relistable(paramsList))

myFunc <- function (params) {
     params <- relist(params, skeleton = paramsList)
     p1 <- params$p1
     p2 <- params$p2
     p3 <- params$p3
     p4 <- params$p4
     ...
}

For another example have a look at the online help file of relist().

I hope it helps.

Best,
Dimitris


On 8/24/2011 9:28 AM, Eran Eidinger wrote:
> Hello,
>
> I have a function with a long list of parameters (of different types,
> numeric and string)
>
> myFunc<-function(p1, p2, p3, p4, p5...etc)
> {
>     do.something(p1,p2,....)
> }
>
> I want to loop over this to provide a different set of parameters to the
> list every time.
>
> for (ii in 1:N)
> {
>     myFunc(p1(ii), p2(ii),....etc)
> }
>
> I would like to simplify the notation and use some kind of structure, maybe
> a list or dataframe.
> However when I try, for example, the following:
>
> params = data.frame(cbind(p1=c(1,2,3), p2=5, p3=c(3,2,1)))
> myFunc<-function(params)
> {
>     attach(params)
>     do.something(p1,p2,....)
>     detach(params)
> }
> for (ii in 1:N)
> {
>     myFunc(params[ii,])
> }
>
>
> do.something fails because p1, p2,... are now factors, and i have to
> as.numeric() or as.char() each parameter before applying mathematical
> operators (such as simple multiplication).
> This defeats the purpose of simplifying the code.
>
> Is there any decent, simple way of doing this?
> Can I unfactor a row of a data.frame? or a list?
> (BTW, "as.numeric()" won't work since some of the parameters
are strings,
> same goes for stringsAsFactors in data.frame)
>
> Thanks,
> Eran
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
Web: http://www.erasmusmc.nl/biostatistiek/