On Fri, 14 Mar 2003, Edmond Ng wrote:
> Hi all,
>
> I have written a program which performs some data simulation, model fitting (to the
> simulated data) and then it will save the parameter estimates from each loop into a
> matrix for later use. Because convergence will not be met in some sets of the
> simulated data, I have used a 'while' instead of a 'for' loop for the job. With a
> 'for' loop I was not able to turn the counter back and repeat the same loop when
> non-convergence occurred.
>
> While my programme seems to be working alright, something rather odd is happening. A
> sample of my programme is as follows:- (the eaxct codes in 'single quotes' have been
> omitted for simplicity sake)
>
> ilim <- 10
> while (i <= ilim) {
> y <- 'simulated some data'
> modelsummary <- try('fitted a model to the simulated data')
> on.exit( c( cat("non-convergence met at loop ", i) , next) )
> i <- i+1
> }
>
> When this stopped, it stopped with the warning message that I provided
> and the number of i was 11. I can't figure out why it is equal to 11
> because the condition for the while loop should have failed when i
> became 11. The loop should have stopped and it should not have got to
> the 'on.exit' bit in the loop automatically.
>
It did stop. It then exited the loop. As it was exiting, it ran the
on.exit you provided. I don't know why you didn't get the error
Error: No loop to break from, jumping to top level
but then I don't know what your code really looked like
For an example of the phenomenon that actually runs, consider
f<-function ()
{
i <- 1
while (i < 10) {
on.exit(cat("exited in iteration", i, "\n"))
cat(i, "\n")
i <- i + 1
}
}
Also, the on.exit() could never do what you want, since you have prevented
any non-convergence errors by using try(). You probably want something
like
if (inherits(modelsummary,"try-error")) {cat("convergence error",i)}
but it's hard to tell.
-thomas
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