[R] updating n within for(i in 1:n) loop

[Prasad, Rajiv]

Thanks to all who replied.  the while construct worked perfectly for my
problem.

Rajiv
--------
Rajiv Prasad
Postdoctoral Research Associate, Hydrology Group
Pacific Northwest National Laboratory, P.O. Box 999, MSIN K9-33
Richland, WA 99352
Voice: (509) 375-2096  Fax: (509) 372-6089  Email: rajiv.prasad at pnl.gov


> -----Original Message-----
> From: Ravi Varadhan [mailto:rvaradha at jhsph.edu]
> Sent: Monday, August 26, 2002 1:01 PM
> To: Prasad, Rajiv
> Cc: R-Help (E-mail)
> Subject: Re: [R] updating n within for(i in 1:n) loop
> 
> 
> 
> Why not use a "while" loop instead?
> 
> n <- 2
> i <- 1
>  while (i <= n)
>  {
>    cat(paste("i =", i, "\n")); flush.console()
>    n <- 5  # version 1
>    i <- i+1
>   }
> 
> I think the above should work.
> 
> Ravi.
> 
> 
> ----- Original Message -----
> From: "Prasad, Rajiv" <Rajiv.Prasad at pnl.gov>
> Date: Monday, August 26, 2002 1:54 pm
> Subject: [R] updating n within for(i in 1:n) loop
> 
> > Hi folks:
> > 
> > I think I'm having problems with figuring this one out:
> > 
> > test1 <- function()
> > {
> >  n <- 2
> > 
> >  for(i in 1:n)
> >  {
> >    cat(paste("i =", i, "\n")); flush.console()
> >    n <- 5  # version 1
> >    #n <<- 5  # version 2
> >    #assign("n", 5, envir = environment(test1))  # version 3
> >  }
> > }
> > 
> > I need the for(.) loop to run (say) n=5 times within the function, 
> > but I do
> > not know that before the loop begins.  In other words, n is to be 
> > updatedduring computations within the for(.) loop.  This code 
> > prints "i = 1" and "i
> > = 2" only.  If I modify test1(.) to use version 2 or 
> version 3 of the
> > assignment, there is no change to the output, and I end up with an 
> > "n" in
> > the parent environment with value 5.  So the problem is to assign 
> > 5 to n in
> > the calling environment of the for(.) loop??  (I'm sure my 
> > terminology is
> > quite mixed up here -- please feel free to comment.)
> > 
> > How do I do this?
> > 
> > Thanks in advance.
> > 
> > > version
> >         _              
> > platform i386-pc-mingw32
> > arch     i386           
> > os       mingw32        
> > system   i386, mingw32  
> > status                  
> > major    1              
> > minor    5.1            
> > year     2002           
> > month    06             
> > day      17             
> > language R              
> > 
> > 
> > Rajiv
> > --------
> > Rajiv Prasad
> > Postdoctoral Research Associate, Hydrology Group
> > Pacific Northwest National Laboratory, P.O. Box 999, MSIN K9-33
> > Richland, WA 99352
> > Voice: (509) 375-2096  Fax: (509) 372-6089  Email: 
> > rajiv.prasad at pnl.gov
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