updating n within for(i in 1:n) loop

-----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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