R help - Apr 2012 - rpart error message

Hi R-helpers,
 I am using rpart package for decision tree using R.We are invoking R
environment through JRI from our java application.Hence, the result of R
command is returned in REXP and we use geterrMessage() to retrieve the
error.

When we execute the following command,

cnr_model<-rpart(as.factor(Species)~Sepal Length+Sepal Width+Petal Length,
method="class", parms=list(split="gini",prior=c()),
control=rpart.control(minsplit=2,
na.action=na.pass,cp=0.001,usesurrogate=1,maxsurrogate=2,surrogatestyle=0,maxdepth=20,xval=10))

we get an error message* "Error: unexpected symbol in
"a<-cnr_model<-rpart(as.factor(Species)~Sepal Length""*

The REXP returned in not null and the geterrMessage() call doesnt return an
error message.

But for other errors in R , say "summary(cnr_model)" , REXP returned
is null
and we get the following error message from geterrMessage() call.

*Error in summary(cnr_model) : object 'cnr_model' not found*

Is this behavior of showing error message specific to rpart package ? Why is
this difference in the way error message is displayed in rpart package?Can
you please let us know how to retrieve error messages of rpart command
through JRI? 

Thanks in advance.

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On Apr 3, 2012, at 4:16 AM, Raji wrote:
> Hi R-helpers,
> I am using rpart package for decision tree using R.We are invoking R
> environment through JRI from our java application.Hence, the result  
> of R
> command is returned in REXP and we use geterrMessage() to retrieve the
> error.
>
> When we execute the following command,
>
> cnr_model<-rpart(as.factor(Species)~Sepal Length+Sepal Width+Petal  
> Length,
You have spaces in your variable names. That has nothing to do with  
JRI and everything to do with base R syntax.

(You also have no data argument so are you attaching it. That would  
seem to be an unwise choice.)
> method="class", parms=list(split="gini",prior=c()),
> control=rpart.control(minsplit=2,
> na 
> .action 
> = 
> na 
> .pass 
> ,cp 
> = 
> 0.001 
> ,usesurrogate=1,maxsurrogate=2,surrogatestyle=0,maxdepth=20,xval=10))
>
> we get an error message* "Error: unexpected symbol in
> "a<-cnr_model<-rpart(as.factor(Species)~Sepal
Length""*
The unexpected symbol was "Length". Spaces are separators to the R  
parser.
>
> The REXP returned in not null and the geterrMessage() call doesnt  
> return an
> error message.
>
> But for other errors in R , say "summary(cnr_model)" , REXP
returned
> is null
> and we get the following error message from geterrMessage() call.
>
> *Error in summary(cnr_model) : object 'cnr_model' not found*
Right. It wasn't found because the command you tried to create it  
with ... failed.
>
> Is this behavior of showing error message specific to rpart package ?
No. It would be very generic.
> Why is
> this difference in the way error message is displayed in rpart  
> package?Can
> you please let us know how to retrieve error messages of rpart command
> through JRI?
>
> Thanks in advance.
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/rpart-error-message-tp4528104p4528104.html
> Sent from the R help mailing list archive at Nabble.com.
>
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David Winsemius, MD
West Hartford, CT