Try Giving Invalid Argument Type Error

Dear R Helpers,

I am getting an error message from the try function that I don't
understand so I am hoping that someone can help.

I am scraping from web pages, but sometimes they disappear.  When that
happens I need to control for it with some sort of function.

This web page is parsed without a problem.

exh<-"NASDAQ"
tic<-"EGHT"
URL<-paste("http://www.advfn.com/p.php?pid=financials&btn=istart_date&mode=quarterly_reports&symbol= 
",
exh,"%3A",tic,"&istart_date=0", sep = "")
doc <- htmlParse(URL)

However, when I change the value of tic it will not.

tic<-"AACOU"
URL<-paste("http://www.advfn.com/p.php?pid=financials&btn=istart_date&mode=quarterly_reports&symbol= 
",
exh,"%3A",tic,"&istart_date=0", sep = "")
doc <- htmlParse(URL)
Error in htmlParse(URL) :
 error in creating parser for
http://www.advfn.com/p.php?pid=financials&btn=istart_date&mode=quarterly_reports&symbol=NASDAQ0X1.CP-1072AACOU&istart_date=0

I tried to account for this using the try function but I get the error
below that I don't understand.

options(error = expression(NULL))
URL<-paste("http://www.advfn.com/p.php?pid=financials&btn=istart_date&mode=quarterly_reports&symbol= 
",
exh,"%3A",tic,"&istart_date=0", sep = "")
if(
!is(
try(
doc <- htmlParse(URL)
,"try-error")
)
)

{
qtrstop <- xpathApply(doc, "count(//select/option)")-5
}
Error in !silent : invalid argument type
Generally one needs to test for inherits(try(...), "try-error")

See last example in ?try
David
>
>
> Any help would be most appreciated.
>
> --John Sparks
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT

Try Giving Invalid Argument Type Error

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