[R] help on using try() to catch an error

[Prof Brian Ripley]

Neither of reduced_model not full_model will ever be NULL.  If this 
fails, they inherit from class "try-error".  See ?try.

So you want

inherits(reduced_model, "try-error") || inherits(full_model, "try-error")


On Thu, 14 Feb 2008, Juliet Hannah wrote:

> Dear R Users,
>
> I have the following glm, which I am running several times in a loop
> (I am not including the full code):
>
> reduced_model <- NULL;
> full_model <- NULL;
> reduced_model <- try(glm.fit(X4,n,family=poisson(link="log")))
> full_model <- try(glm.fit(X5,n,family=poisson(link="log")));
>
> On some occasions, an error is produced, which is why I have attempted
> to work around this with try().
>
> I then have the following statement, which checks if full_model or
> reduced_model are still NULL.
>
> if (is.null(reduced_model) || is.null(full_model)) p <- NA else p <-
> pchisq(reduced_model$deviance - full_model$deviance,
> reduced_model$df.residual - full_model$df.residual, lower.tail=
> FALSE);
>
> This is not solving my problem meaning my program still stops and
> gives me the following error:
>
> Error in ifelse(y == 0, 1, y/mu) : dim<- : dims [product 9] do not
> match the length of object [18]
> Error in pmatrix[perm, ] <- apply(pairs.subset, 1, getLRTp2) :
>        nothing to replace with
>
>
> Can you help me figure out what I have done incorrectly?
>
> Thanks for your time,
>
> Juliet
>
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> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595