[R] how does while work

[Liaw, Andy]

Don't think so.  stop() and warning() will only be triggered when explicited
told to do so.  Thus, essentially the (only?) idiotic way to do it is insert
if(x>=100) stop("x>100!") everywhere.  There's no mechanism to keep track of
a variable as the program executes, AFAIK.

Andy

> -----Original Message-----
> From: Giovanni Petris [mailto:GPetris at uark.edu]
> Sent: Thursday, March 21, 2002 3:17 PM
> To: andy_liaw at merck.com
> Cc: richmond at saintmarys.edu; imij at columbus.rr.com;
> r-help at stat.math.ethz.ch
> Subject: Re: [R] how does while work
> 
> 
> 
> Maybe warning() or stop() can be used for this purpose.
> 
> Giovanni
> 
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> > From: "Liaw, Andy" <andy_liaw at merck.com>
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> > What he wanted is a mechanism to "watch" for a condition on 
> a variable, and
> > stop execution as soon as that condition is TRUE, 
> regardless of where in the
> > program.  The only thing that I know of that sort of does 
> this is inside
> > gdb, the GNU debugger.  AFAIK this is impossible.  If 
> anyone has better
> > idea, I'd like to hear about it, too.
> > 
> > Andy
> > 
> > > -----Original Message-----
> > > From: David A Richmond [mailto:richmond at saintmarys.edu]
> > > Sent: Thursday, March 21, 2002 11:00 AM
> > > To: jimi adams
> > > Cc: r-help at stat.math.ethz.ch
> > > Subject: Re: [R] how does while work
> > > 
> > > 
> > > 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?
> > > 
> > > daver
> > > 
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> -- 
> 
>  __________________________________________________
> [                                                  ]
> [ Giovanni Petris                 GPetris at uark.edu ]
> [ Department of Mathematical Sciences              ]
> [ University of Arkansas - Fayetteville, AR 72701  ]
> [ Ph: (479) 575-6324, 575-8630 (fax)               ]
> [ http://definetti.uark.edu/~gpetris/              ]
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