R help - Jul 2009 - how to avoid a for looping break after an error message

Hi all,
I wrote a piece of code that generates simulated variables. after variable
generation I use them in several analyzes.
However, when I use a for to repeat the procedure 1000 times I get an erro
message in one of the "for" steps, precisely at this time:
gls.temp<- gls(y2 ~ x2,correlation=corExp(form=~coord2[,1]+coord2[,2]))  #
coord 2 are spatial coordinates
and the error message is:
Error in gls(y2 ~ x2, correlation = corExp(form = ~coord2[, 1] + coord2[,
:  false convergence (8)
I don´t know what causes this error. My problem is that this error stops all
the calculations during the for looping and all previous results are lost.
Can anyone help me to avoid that my looping stops after the error message?
Thanks in advance,
Victor Landeiro

PS: A reproducible example is above, but there is a chance that the error
message do not appears, and i reaches 1000:
for(i in 1:1000){
x<-sample(seq(10,n*10,10)+runif(n,-2,2))
    coord<-cbind(seq(10,n*10,10),rep(1,n))
    x<-sort(x)
    colnames(coord)<-c("X","Y")
    y=(1+0.8*x)+runif(n,-(n*3),(n*3))
    x2<-rep(x,each=nn)+rnorm(n*nn,0,2)
    y2<-rep(y,each=nn)+rnorm(n*nn,0,2)
    coord2<-cbind(rep(coord[,1],each=nn)+rnorm(n*nn),rep(1,n*nn))

gls<- gls(y2 ~ x2,correlation=corGaus(form=~coord2[,1]+coord2[,2]))
print(i)
}
-- 
Victor Lemes Landeiro
Instituto Nacional de Pesquisas da Amazônia - INPA - CPEc (Ecologia)
Av. André Araujo, 2936, Petrópolis
CEP: 69067-375
Manaus, Amazonas, Brasil
Telefones: INPA (92) 3643 1912
Casa (92) 3646 3942 ou 3304 3942
Celular (92) 88311121
www.inpa.gov.br
http://ppbio.inpa.gov.br
http://ppbio.inpa.gov.br/Port/public/disciplinas2/Introducao%20ao%20R%202009.pdf

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Victor Landeiro wrote:
> 
> Hi all,
> I wrote a piece of code that generates simulated variables. after variable
> generation I use them in several analyzes.
> However, when I use a for to repeat the procedure 1000 times I get an erro
> message in one of the "for" steps, precisely at this time:
> gls.temp<- gls(y2 ~ x2,correlation=corExp(form=~coord2[,1]+coord2[,2])) 
#
> coord 2 are spatial coordinates
> and the error message is:
> Error in gls(y2 ~ x2, correlation = corExp(form = ~coord2[, 1] + coord2[,
> :  false convergence (8)
> I don?t know what causes this error. My problem is that this error stops
> all
> the calculations during the for looping and all previous results are lost.
> Can anyone help me to avoid that my looping stops after the error message?
> Thanks in advance,
> Victor Landeiro
> 
> <snip>
> 
> 
You could wrap the offending function in the try statement:

gls.temp <- try(  gls(y2 ~
x2,correlation=corExp(form=~coord2[,1]+coord2[,2]))  )

Then you want to check the class of gls.temp- if it is a "try-error",
the
data you are expecting will not be there:

if( class(gls.temp) == 'try-error' ){

  # You had an error, maybe just skip this iteration using next

}else{

  # It's all good- do your normal calculations  

}

Hope that helps!

-Charlie

-----
Charlie Sharpsteen
Undergraduate
Environmental Resources Engineering
Humboldt State University
-- 
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