R help - Mar 2011 - tryCatch - Continuing for/next loop after error

Dear all,

I am not sure I understand fully the functionality of "tryCatch" and 
"try" commands and how these are used to continue a for/next loop if
an
error occurs within the loop.

Can somebody point me to material (or share some code) with more 
extensive examples than the ones in the help/FAQ pages?

Do explain my problem in more detail:

for (i in 100:1000)
{
      ## do some other stuff

     dataset<-head(data,i)
     tryCatch(estimatemodel(dataset))

}

My for/next loop reads in data (increasing the dataset by one point at 
every loop run) and then estimates a model. When the problem is 
computationally singular, the loop exits. I want to continue the loop 
and register an "error" estimation value for that step. However when I
use use the try tryCatch(estimatemodel(data)) (where estimatemodel() is 
a wrapper function calling the model estimation and optimization 
routines), the problem still persists.

Is this the correct way to use tryCatch (or try) or should these go 
inside the actual code bits (i.e., in a more low level fashion) that 
conduct the optimization and model estimation?

Apologies if this is not clear enough.

Best,
Costas

--------------------------------------
Jonathan P. Daily
Technician - USGS Leetown Science Center
11649 Leetown Road
Kearneysville WV, 25430
(304) 724-4480
"Is the room still a room when its empty? Does the room,
 the thing itself have purpose? Or do we, what's the word... imbue it."
     - Jubal Early, Firefly

r-help-bounces at r-project.org wrote on 03/10/2011 03:51:15 AM:
> [image removed] 
> 
> [R] tryCatch - Continuing for/next loop after error
> 
> Costas 
> 
> to:
> 
> r-help
> 
> 03/10/2011 03:53 AM
> 
> Sent by:
> 
> r-help-bounces at r-project.org
> 
> Please respond to costas.vorlow
> 
> Dear all,
> 
> I am not sure I understand fully the functionality of "tryCatch"
and
> "try" commands and how these are used to continue a for/next loop
if an
> error occurs within the loop.
> 
> Can somebody point me to material (or share some code) with more 
> extensive examples than the ones in the help/FAQ pages?
> 
> Do explain my problem in more detail:
> 
> for (i in 100:1000)
> {
>       ## do some other stuff
> 
>      dataset<-head(data,i)
>      tryCatch(estimatemodel(dataset))
if estimatemodel returns an error (i.e. via a call to stop()), then this 
should break out of the loop:

tryCatch(estimatemodel(dataset), error = function() break)

if you want to skip to the next iteration, use:
tryCatch(estimatemodel(dataset), error = function() next)
> 
> }
> 
> My for/next loop reads in data (increasing the dataset by one point at 
> every loop run) and then estimates a model. When the problem is 
> computationally singular, the loop exits. I want to continue the loop 
> and register an "error" estimation value for that step. However
when I
> use use the try tryCatch(estimatemodel(data)) (where estimatemodel() is 
> a wrapper function calling the model estimation and optimization 
> routines), the problem still persists.
> 
> Is this the correct way to use tryCatch (or try) or should these go 
> inside the actual code bits (i.e., in a more low level fashion) that 
> conduct the optimization and model estimation?
> 
> Apologies if this is not clear enough.
> 
> Best,
> Costas
> 
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