Re: [R] The fastest way to select and execute a few selected functions inside a function

From: Ferdinand Alimadhi <falimadhi_at_iq.harvard.edu>
Date: Thu 15 Dec 2005 - 12:35:56 EST

Is this what you want?

myf<-function(FUN, x){

            res<- vector( mode="list")
            for(i in FUN)
                        res[[i]]<-do.call(i,args=list(x))
            return(res)

}
 > myf(FUN="mean",x=1:10)
 > myf(FUN=c("mean","max"),x=1:10)
 > myf(FUN=c("mean","max", "sum", "median"),x=1:10)




Ales Ziberna wrote:

>Dear useRs?
>
>
>
>I have the following problem! I have a function that calls one or more
>functions, depending on the input parameters. I am searching for the fastest
>way to select and execute the selected functions and return their results in
>a list. The number of possible functions is 10, however usually only 2 are
>selected (although sometimes more, even all).
>
>
>
>For examples, if I have function "myf" and the possible functions that I
>want to call are "mean", "max" and "sum". I have thought of one way (myf) to
>do that and am interested if there maybe exists a faster way (the speed is
>very important, since this can be repeated millions of times in my
>function).
>
>
>
>
>
>myf<-function(FUN, x){
>
> f<-list(mean=mean, max=max, sum=sum)
>
> res<- vector( mode="list")
>
> for(i in FUN){
>
> res[[i]]<-f[[i]](x)
>
> }
>
> return(res)
>
>}
>
>myf(FUN=c("mean","max"),x=1:10)
>
>
>
>
>
>In this case, it would be faster if I would compute all functions, even if I
>need only one:
>
>myf.all<-function(x){
>
> list(mean=mean(x), max=max(x), sum=sum(x))
>
>}
>
>
>
>
>
>>gc();system.time(for(i in 1:10000)myf.all(1:20))
>>
>>
>
> used (Mb) gc trigger (Mb) max used (Mb)
>
>Ncells 165659 4.5 350000 9.4 350000 9.4
>
>Vcells 61135 0.5 786432 6.0 283043 2.2
>
>[1] 0.90 0.00 1.08 NA NA
>
>
>
>>gc();system.time(for(i in 1:10000)myf(FUN="mean",1:20))
>>
>>
>
> used (Mb) gc trigger (Mb) max used (Mb)
>
>Ncells 165659 4.5 350000 9.4 350000 9.4
>
>Vcells 61135 0.5 786432 6.0 283043 2.2
>
>[1] 1.14 0.00 1.40 NA NA
>
>
>
>This does (usually) not happen in my case, since most of functions I
>consider are more complex.
>
>
>
>Thanks in advance for any suggestions!
>
>
>Best regards,
>
>Ales Ziberna
>
>______________________________________________
>R-help@stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>
>

-- 
Ferdinand Alimadhi
Programmer / Analyst
Harvard University
The Institute for Quantitative Social Science
(617) 496-0187
falimadhi@latte.harvard.edu
www.iq.harvard.edu


	[[alternative HTML version deleted]]

______________________________________________
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Received on Thu Dec 15 12:45:52 2005

This archive was generated by hypermail 2.1.8 : Thu 15 Dec 2005 - 14:35:48 EST