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

[Ravi Varadhan]

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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