R help - Feb 2011 - monitor variable change

Dear all I would like to ask you if there is a way in R to monitor in R when a
value changes.

Right now I use the sprintf('my variables is %d \n, j) to print the value of
the variable.

Is it possible when a 'big' for loop executes to open in a new window to
dynamically check only the variable I want to.

If I put all the sprintf statements inside my loop then I get flooded with so
many messages that makes it useless.

Best Regards
Alex

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On 02/16/2011 10:38 AM, Alaios wrote:
> Dear all I would like to ask you if there is a way in R to monitor in R
when a value changes.
> 
> Right now I use the sprintf('my variables is %d \n, j) to print the
value of the variable.
> 
> Is it possible when a 'big' for loop executes to open in a new
window to dynamically check only the variable I want to.
I don't think that this functionality is implemented.

But I guess you can implement it - would it be possible to re-define th
"<-" to check if a certain variable is to be changed, and then
print it?

Might be tricky and would slow everything considerably down.

Just a thought,

Rainer
> 
> If I put all the sprintf statements inside my loop then I get flooded with
so many messages that makes it useless.
> 
> Best Regards
> Alex
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Natural Sciences Building
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Skype:      RMkrug
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One way to implement this functionality is with a task manager callback:

watch <- function(varname) {
  old <- get(varname)

  changed <- function(...) {
    new <- get(varname)
    if (!identical(old, new)) {
      message(varname, " is now ", new)
      old <<- new
    }
    TRUE
  }
  invisible(addTaskCallback(changed))
}

a <- 1
watch("a")
a <- 2


Hadley

On Wed, Feb 16, 2011 at 9:38 AM, Alaios <alaios at yahoo.com>
wrote:
> Dear all I would like to ask you if there is a way in R to monitor in R
when a value changes.
>
> Right now I use the sprintf('my variables is %d \n, j) to print the
value of the variable.
>
> Is it possible when a 'big' for loop executes to open in a new
window to dynamically check only the variable I want to.
>
> If I put all the sprintf statements inside my loop then I get flooded with
so many messages that makes it useless.
>
> Best Regards
> Alex
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/