R help - Sep 2001 - on.exit

Hola!

look at the following:
> test <- function() {
+    options(warn=-1)
+    on.exit( options(warn=0))
+    log(-1)
+ }
> test()
[1] NaN


but what should be better, doesnt work:
> test1 <- function() {
+    oldwarn <- options("warn")
+    options(warn=-1)
+    on.exit( options(warn=oldwarn))
+    log(-1)
+ }
> test1()
Error in options(...) : warn parameter invalid
> 

What is wrong? (I have tried other versions, without success)

Kjetil Halvorsen.
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On Thu, 27 Sep 2001 13:05:01 -0400, you wrote in message
<3BB35C3C.C4FE9451 at umsanet.edu.bo>:

>but what should be better, doesnt work:
>
>> test1 <- function() {
>+    oldwarn <- options("warn")
>+    options(warn=-1)
>+    on.exit( options(warn=oldwarn))
>+    log(-1)
>+ }
>> test1()
>Error in options(...) : warn parameter invalid
>> 
>
>
>What is wrong? (I have tried other versions, without success)
The problem is that you're assuming options() behaves the way par()
does, i.e. that options("warn") returns a number.  It doesn't, it
returns a list.  

The simplest way to get what you want is probably

test1 <- function() {
    oldwarn <- options(warn=-1)   # first call
    on.exit( options(oldwarn))       # second call
    log(-1)
}

Notice that the first call that changes the option returns the old
value, so you don't need two calls at the start; the second call that
restores it just uses the list (which has the name of the option
embedded in it).

Duncan Murdoch
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kjetil halvorsen <kjetilh at umsanet.edu.bo> writes:
> but what should be better, doesnt work:
> 
> > test1 <- function() {
> +    oldwarn <- options("warn")
> +    options(warn=-1)
> +    on.exit( options(warn=oldwarn))
> +    log(-1)
> + }
> > test1()
> Error in options(...) : warn parameter invalid
> > 
> 
> 
> What is wrong? (I have tried other versions, without success)
oldwarn is a list. Try
> fix(test1)
>  test1()
[1] NaN
> test1
function() {
  oldwarn <- options("warn")
  options(warn=-1)
  on.exit( options(warn=oldwarn$warn))
  log(-1)
}

or maybe 

oldwarn <- unlist(options("warn")) 
... 
on.exit(options(warn=oldwarn))

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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