[R] tryCatch with integration

[William Dunlap]

You want the error= argument to tryCatch to be the function
that computes the intergral by the backup method.  The finally=
argument is treated as an expression (not a function) that is
evaluated (not called) after all the other work in tryCatch has
been done.  The value of the evaluated finally expression appears
to be ignored.

E.g.,

  > z <- tryCatch({message("Calling seq_len"); seq_len(-1)},
  +    error=function(cond){message("Encountered an error: ", cond) ; integer(0)},
  +    finally={message("Finally"); NA})
  Calling seq_len
  Encountered an error: Error in seq_len(-1): argument must be coercible to non-negative integer

  Finally
  > z
  integer(0)

or, the same example with a main expression that does not throw an error,

  > z <- tryCatch({message("Calling seq_len"); seq_len(7)},
  +    error=function(cond){message("Encountered an error: ", cond) ; integer(0)},
  +    finally={message("Finally"); NA})
  Calling seq_len
  Finally
  > z
  [1] 1 2 3 4 5 6 7

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com 

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of statfan
> Sent: Sunday, October 30, 2011 6:24 PM
> To: r-help at r-project.org
> Subject: [R] tryCatch with integration
> 
> I am trying to compute the approximate numerical integration of the following
> expression using the integrate function:
> 
> 
> > 	(integrate(function(x) {log(1+x^2)*(1+x^2)^(-20.04543)},low,Inf)$val)
> Error in integrate(function(x) { : the integral is probably divergent
> 
> 
> which gives me an error.  If this error happens I want to return the
> following instead
> 
> > (area(function(x) {-2*log(cos(x))*(cos(x)^(2*e-2))}, atan(low), pi/2))
> [1] 0.01045636
> 
> In order to accomplish this I tried the following:
> 
> > this=	tryCatch((integrate(function(x)
> > {log(1+x^2)*(1+x^2)^(-e)},low,Inf)$val),error=function(e) e, finally =
> > (area(function(x) {-2*log(cos(x))*(cos(x)^(2*e-2))}, atan(low), pi/2)))
> > this
> <simpleError in integrate(function(x) {    log(1 + x^2) * (1 + x^2)^(-e)},
> low, Inf): the integral is probably divergent>
> 
> Perhaps I am using tryCatch incorrectly? Any help would be greatly
> appreciated.
> 
> --
> View this message in context: http://r.789695.n4.nabble.com/tryCatch-with-integration-
> tp3954528p3954528.html
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> 
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