Florin Maican
2009-Mar-26 15:17 UTC
[R] programming creating different functions in a loop
Hi
I want to create the following functions in a loop
f1<-function(x){x+1}
f2<-function(x){x+2}
f3<-function(x){x+3}
Output f1(2)=3
f2(2)=4
f3(2)=5
I tried to create the in a loop as bellow but I get wrong on answers
because the value of i change
for(i in 1:3){
assign(paste("f",i,sep="")
,function(x)
x+i
)
} # end for
Output f1(2)=5
f2(2)=5
f3(2)=5
But it is not what I want. The question is how I can
fix in R the value of "i" in my functions? I tried to use assign()
and
get(),but I did not manage.
Thanks in advance,
Florin
--
Florin Maican
=================================
Department of Economics,
School of Business, Economics and Law,
Gothenburg University, Sweden
-----------------------------------
P.O. Box 640 SE-405 30,
Gothenburg, Sweden
Mobil: +46 76 235 3039
Phone: +46 31 786 4866
Fax: +46 31 786 4154
Home Page: http://maicanfg.googlepages.com/index.html
E-mail: florin.maican at handels.gu.se
------------------------------------
"Not everything that counts can be
counted, and not everything that can be
counted counts."
--- Einstein ---
luke at stat.uiowa.edu
2009-Mar-26 15:57 UTC
[R] programming creating different functions in a loop
for() does not creae separete bindings for the index each iteration,
so the function bodies see the global binding of i, which in this case
will be the final value. One possible solution is to use local(), e.g.
for(i in 1:3){
assign(paste("f",i,sep=""),
local({
k <- i # create local binding with current loop index value
function(x) x + k
}))
}
luke
On Thu, 26 Mar 2009, Florin Maican wrote:
> Hi
>
> I want to create the following functions in a loop
>
> f1<-function(x){x+1}
> f2<-function(x){x+2}
> f3<-function(x){x+3}
>
> Output f1(2)=3
> f2(2)=4
> f3(2)=5
>
>
> I tried to create the in a loop as bellow but I get wrong on answers
> because the value of i change
>
> for(i in 1:3){
> assign(paste("f",i,sep="")
> ,function(x)
> x+i
> )
> } # end for
>
> Output f1(2)=5
> f2(2)=5
> f3(2)=5
> But it is not what I want. The question is how I can
> fix in R the value of "i" in my functions? I tried to use
assign() and
> get(),but I did not manage.
>
> Thanks in advance,
> Florin
>
>
--
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke at stat.uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
Florin Maican
2009-Mar-26 16:16 UTC
[R] programming creating different functions in a loop
Thanks Luke! It works! My mistake was that I used "local binding" only for "i" and not for the whole function. Best regards, Florin On Thu, 26 Mar 2009 10:57:21 -0500 (CDT) luke at stat.uiowa.edu wrote:> for() does not creae separete bindings for the index each iteration, > so the function bodies see the global binding of i, which in this case > will be the final value. One possible solution is to use local(), > e.g. > > for(i in 1:3){ > assign(paste("f",i,sep=""), > local({ > k <- i # create local binding with current loop > index value function(x) x + k > })) > } > > > luke > > > On Thu, 26 Mar 2009, Florin Maican wrote: > > > Hi > > > > I want to create the following functions in a loop > > > > f1<-function(x){x+1} > > f2<-function(x){x+2} > > f3<-function(x){x+3} > > > > Output f1(2)=3 > > f2(2)=4 > > f3(2)=5 > > > > > > I tried to create the in a loop as bellow but I get wrong on answers > > because the value of i change > > > > for(i in 1:3){ > > assign(paste("f",i,sep="") > > ,function(x) > > x+i > > ) > > } # end for > > > > Output f1(2)=5 > > f2(2)=5 > > f3(2)=5 > > But it is not what I want. The question is how I can > > fix in R the value of "i" in my functions? I tried to use assign() > > and get(),but I did not manage. > > > > Thanks in advance, > > Florin > > > > >-- Florin G. Maican ================================= Ph.D. candidate, Department of Economics, School of Business, Economics and Law, Gothenburg University, Sweden ----------------------------------- P.O. Box 640 SE-405 30, Gothenburg, Sweden Mobil: +46 76 235 3039 Phone: +46 31 786 4866 Fax: +46 31 786 4154 Home Page: http://maicanfg.googlepages.com/index.html E-mail: florin.maican at handels.gu.se ------------------------------------ "Not everything that counts can be counted, and not everything that can be counted counts." --- Einstein ---
Anytime that you are tempted to use assign and a loop, you should consider using lapply (or sapply) and a list instead. Consider this alternative:> f <- lapply( 1:3, function(i){ force(i); function(x) x+i} ) > > f[[1]](3)[1] 4> f[[2]](10)[1] 12> f[[3]](0)[1] 3> > sapply( f, function(f) f(1:10) )[,1] [,2] [,3] [1,] 2 3 4 [2,] 3 4 5 [3,] 4 5 6 [4,] 5 6 7 [5,] 6 7 8 [6,] 7 8 9 [7,] 8 9 10 [8,] 9 10 11 [9,] 10 11 12 [10,] 11 12 13 Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.snow at imail.org 801.408.8111> -----Original Message----- > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r- > project.org] On Behalf Of Florin Maican > Sent: Thursday, March 26, 2009 9:18 AM > To: r-help at r-project.org > Subject: [R] programming creating different functions in a loop > > Hi > > I want to create the following functions in a loop > > f1<-function(x){x+1} > f2<-function(x){x+2} > f3<-function(x){x+3} > > Output f1(2)=3 > f2(2)=4 > f3(2)=5 > > > I tried to create the in a loop as bellow but I get wrong on answers > because the value of i change > > for(i in 1:3){ > assign(paste("f",i,sep="") > ,function(x) > x+i > ) > } # end for > > Output f1(2)=5 > f2(2)=5 > f3(2)=5 > But it is not what I want. The question is how I can > fix in R the value of "i" in my functions? I tried to use assign() and > get(),but I did not manage. > > Thanks in advance, > Florin > > -- > Florin Maican > =================================> > Department of Economics, > School of Business, Economics and Law, > Gothenburg University, Sweden > ----------------------------------- > P.O. Box 640 SE-405 30, > Gothenburg, Sweden > > Mobil: +46 76 235 3039 > Phone: +46 31 786 4866 > Fax: +46 31 786 4154 > Home Page: http://maicanfg.googlepages.com/index.html > E-mail: florin.maican at handels.gu.se > ------------------------------------ > "Not everything that counts can be > counted, and not everything that can be > counted counts." > --- Einstein --- > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting- > guide.html > and provide commented, minimal, self-contained, reproducible code.