[R] tryCatch - Continuing for/next loop after error

[Jonathan P Daily]

--------------------------------------
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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