Re: [R] how to use try()

Spencer Graves Tue, 10 Feb 2004 11:10:30 -0800

The "try" solutions suggested won't work in S-Plus. If you want transportable code, the following worked for me just now in both S-Plus 6.2 and R 1.8.1:

error <- function()stop()

result <- try(error())
if(regexpr("error", casefold(class(result)))>0)
   "try trapped an error"

     Best Wishes,
     spencer graves

r.ghezzo wrote:

Thanks to everybody who answered my question. Here are the suggestion for completion sake of the archives. from John Fox @ Mcmaster.ca lo <- try(nls(y~y0+a/(1+(x/x0)^b),start=list(y0=0.1,a=a0,x0=x00,b=-8.1))) beta[i] <- if (class(lo) == "try-error") NA else lo$m$getPars()[4]
from Peter Dalgaard @ biostat.ku.dk
Just check the return value from try:
beta[i] <- if(inherits(try(.....),"try-error")) NA else lo$etc...
from Thomas Lumley @ u.washington.edu
You want either both assignments inside the try()
try({
    lo<-nls(....)
    beta[i]<-lo$m$getPars(4)
})
or both outside
lo<- try(nls(....))
if (inherits(lo,"try-error")) beta[i]<-NA else beta[i]<-lo$m$getPars()[4]
from Sundar Dorai-Raj @ pdf.com
if (inherits(lo,"try-error")) beta[i]<-NA else beta[i]<-lo$m$getPars()[4]
also from Andrej Kveder @ zrc-sazu.si; Patric Burns @ pburns.seanet.com
Hadley Wickham @ auckland.ac.nz;
from Douglas Bates @ stat.wisc.edu
Check the function nlsList in package nlme.  It does something very
like what you want to do.
It is not a good idea to use lo$m$getPars() directly.  It is better to
use the generic function, which in this case is coef(), as in
coef(lo)[4]
On Mon, 09 Feb 2004 14:30:07 -0500
 "r.ghezzo" <[EMAIL PROTECTED]> wrote:
Hello, I have a program with this section: .. for(i in 1:20){ lo <- nls(y~y0+a/(1+(x/x0)^b),start=list(y0=0.1,a=a0,x0=x00,b=-8.1)) beta[i] <- lo$m$getPars()[4] } .. If the fit works this is OK but if the fit fails, the whole program fails so: .. for(i in 1:20){ try(lo <- nls(y~y0+a/(1+(x/x0)^b),start=list(y0=0.1,a=a0,x0=x00,b=-8.1))) beta[i] <- lo$m$getPars()[4] } .. but the try catches the error in nls and beta[i] gets assigned beta[i-1] from the previous loop. This is bad but no so bad as it can be checked, Now in some cases the error is in i=1 and the program stops!! is there a way to set lo$m$getPars() to zero before the call? I tried to understand the use of tryCatch() but frankly it is above me. Sorry Thanks for any help Heberto Ghezzo Meakins-Christie Labs

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Re: [R] how to use try()

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