[R] Rprintf not updating

[Erik Wright]

Hi Charlie,

I like your idea of updating an R progress bar from C, but I don't at all understand how to call txtProgressBar from C.  I have looked at Writing R Extensions and it is equally confusing.  Any help would be appreciated.

Thanks!,
Erik


On Apr 5, 2010, at 10:29 AM, Sharpie wrote:

> 
> 
> Erik Wright wrote:
>> 
>> Hello all,
>> 
>> I am using Rprintf in a C for loop (from .Call) to print a progress
>> indicator showing the current percent complete. The loop I am doing is an
>> time intensive call to another function.  I have noticed that Rprintf does
>> not print to the R-window until the entire loop has been completed.  When
>> it reaches the end of the loop it suddenly prints 0 percent to 100 percent
>> in a split second.  For less intensive function calls it prints properly
>> while looping.  My question is this:  is there any way to force Rprintf to
>> print to the screen during a loop?
>> 
>> On a related note, how can I show a percent sign in the output?  For
>> example, Rprintf("0%"); only prints a zero.
>> 
>> Thanks!,
>> Erik
>> 
> 
> Perhaps you could use a callback to R's built in progress bar functions to
> perform this for you in a nicely formatted way.  Something of the form:
> 
>  pBar <- txtProgressBar( min = , max = , type = 3 )
> 
>  cResults <- .Call( 'some_c_routine', some, args, including, pBar )
> 
>  close( pBar )
> 
> Since you pass the progress bar to the C routine, you could perform a
> callback to the R function setTxtProgressBar() to update it every iteration. 
> I posted an example of how to perform callbacks from C to R in this thread:
> 
> 
> http://n4.nabble.com/Writing-own-simulation-function-in-C-td1580190.html#a1580423
> 
> Hope this helps!
> 
> -Charlie
> 
> -----
> Charlie Sharpsteen
> Undergraduate-- Environmental Resources Engineering
> Humboldt State University
> -- 
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