[R] tryCatch question

Luke Tierney luke at stat.uiowa.edu
Thu Aug 14 17:59:35 CEST 2008

Read the argment descriptions and Look at the examples in ?tryCatch.
The `expr' argument (i.e. the code to try) and the `finally' argument
are expressions that are evaluated (via standard lazy evaluation of
arguments).  The error condition handlers, provided as the `...'
argument in errorClass = handler form(s), are functions of one argument,
the error condition.  As in the examples I usualy use fuctions writen
in-line.  There is no non-standard evaluation involved, so standard
scoping rules apply.


On Thu, 14 Aug 2008, rkevinburton at charter.net wrote:

> I would like to use the 'tryCatch' function but am having a hard
   time getting my head around it. In 'C' like languages
   try/catch/finally means try a block of statements and if any throw
   an error then do the statements in the catch block and then error or
   not always do the staements in the finally block. In 'R' as best as
   I can tell the block of staements in the try block is a single
   function. Does this mean I need to construct a temporary function
   that contains what I would have put in the try blck? Also in 'R' it
   seems the 'finally' function (of 'tryCatch' most closely mimics the
   catch block of 'C'. Right? A similar comment on the finally
   function. Do I need to create a temporary function that contains the
   staements that I normally would put in a 'C' like catch clause? If I
   do need to create functions for the try and error conditions what is
   the scope or enviironment that the functions are called under? The
   'try' function is relatively straightforward but when an error
   occurs what variable will I have access to?

> Thank you.
> Kevin
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Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

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