R help - Dec 2007 - way to check if the evaluation of an expression returns an error?

Is there a recommended or "good" way to check if the evaluation of an
expression returns an error?
   
  e.g. 
var(NA)    
  I wish  var(NA) to return NA or "err", or some other value, even a
text-string, but not an error message.
   
   
  I am using a loop to load many samples of data and to perform analysis on each
sample.  On occasion, the function I execute returns an error message.  (e.g.
when all data is NA, etc).   I wish for the loop to continue to execute, and to
have the function return an NA or NULL rather then an error message.
   

       
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?try

Cheers,

Andrew

On Fri, Dec 14, 2007 at 02:10:52PM -0800, Thomas Pujol
wrote:
> Is there a recommended or "good" way to check if the evaluation
of an expression returns an error?
>    
>   e.g. 
> var(NA)    
>   I wish  var(NA) to return NA or "err", or some other value,
even a text-string, but not an error message.
>    
>    
>   I am using a loop to load many samples of data and to perform analysis on
each sample.  On occasion, the function I execute returns an error message. 
(e.g. when all data is NA, etc).   I wish for the loop to continue to execute,
and to have the function return an NA or NULL rather then an error message.
>    
> 
>        
> ---------------------------------
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Andrew Robinson  
Department of Mathematics and Statistics            Tel: +61-3-8344-9763
University of Melbourne, VIC 3010 Australia         Fax: +61-3-8344-4599
http://www.ms.unimelb.edu.au/~andrewpr
http://blogs.mbs.edu/fishing-in-the-bay/