The fastest way to select and execute a few selected functions inside a function

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The fastest way to select and execute a few selected functions inside a function

Ales Ziberna
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

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

Ferdinand Alimadhi
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
>
>______________________________________________
>[hidden email] 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
[hidden email]
www.iq.harvard.edu


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

Ales Ziberna
In reply to this post by Ales Ziberna

----- Original Message -----
From: "Ales Ziberna" <[hidden email]>
To: "R-help" <[hidden email]>
Sent: Wednesday, December 14, 2005 6:05 PM
Subject: The fastest way to select and execute a few selected functions
inside a function


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

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html