[R] how does while work

David A Richmond richmond at saintmarys.edu
Thu Mar 21 17:00:02 CET 2002

On Wed, 20 Mar 2002, jimi adams wrote:

> i am having some problems with a program that i am writing and i think that
> knowing how the while command works will help me to figure out where i am
> going wrong
> *when do you get kicked out of a while loop?*
> (i.e., in the following example  what would the final value of 'a' be?) i
> thought it would be 99 but running it in R i get 101 (and 101 for x too!)
> while (x <100) {
>   for (i in 1:101) {
>     i -> x
>     x -> a
>   }
> *here*  
> }

Essentially the while condition doesn't get checked until just before the
last curly brace (where I inserted *here* above), so the for loop gets to
do it's thing until i (and x and a) reach 101 and only then is the while
condition allowed to drop you out of the loop.

> while this is a crude example, it is the basic form of what i am trying to
> do, and i am guessing that while is not what i am looking for...

what exactly are you trying to do?


|David Richmond                It works on a          |      
+ Dept. of Sociology          complex scientific      + 
|Saint Mary's College          principle, known as    |  
+ Notre Dame, IN 46556               "pot luck."      +
|574-284-4517                    - The Doctor         |

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