[R] Creating a loop with an indefinite end term

[Steve Lavrenz]

Albyn,

Thanks for your help. This however, still assumes that I have to define an
array of length 10. Is there a way that I can construct this so that my
array is exactly as long as the number of spots I need to reach my threshold
value?

Thanks,

-Steve

-----Original Message-----
From: Albyn Jones [mailto:jones at reed.edu] 
Sent: Tuesday, April 10, 2012 11:46 AM
To: Steve Lavrenz
Cc: r-help at r-project.org
Subject: Re: [R] Creating a loop with an indefinite end term

Here are a couple of constructions that work.  

albyn
===========================================

num <- rep(0,10)
for (i in 2:10)   { 
      num[i] <- num[i-1] + 5 
      if(num[i] > 20) break
} 
> num
 [1]  0  5 10 15 20 25  0  0  0  0

or

num <- rep(0,10)
done <- FALSE
i <- 2
while(!done){
     num[i] <- num[i-1] + 5
     if(num[i] > 20) done <- TRUE
     i <- i + 1
}
> num
 [1]  0  5 10 15 20 25  0  0  0  0


On Tue, Apr 10, 2012 at 10:48:34AM -0400, Steve Lavrenz wrote:
> Everyone,
> 
> I'm very new to R, especially when it comes to loops and functions, so 
> please bear with me if this is an elementary question. I cannot seem 
> to figure out how to construct a loop which runs a function until a 
> certain value is computed. For example, say I have the following:
> 
> num = numeric (10)
> num [1] = 0 
> for (i in 2:10)   { 
>       num [i] = num [i-1] + 5
> }
> 
> This adds 5 to the preceding spot of a vector of length 10 to get the 
> value in the current spot. However, say I don't just want to run this 
> for 10 spots; rather I want to run it until a certain value (say, 100) is
computed.
> How I construct my loop to do this? 
> 
> Thanks!
> 
> 
> 	[[alternative HTML version deleted]]
> 
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> 

--
Albyn Jones
Reed College
jones at reed.edu