[R] How to save/load RWeka models into/from a file?

[Achim Zeileis]

On Thu, 16 Oct 2008, Paulo Cortez wrote:

> Hi,
>
> I want to save a RWeka model into a file, in order to retrive it latter with 
> a load function.
>
> See this example:
>
> library(RWeka)
>
> NB <- make_Weka_classifier("weka/classifiers/bayes/NaiveBayes")
> model<-NB(formula,data=data,...) # does not run but you get the idea
>
> save(model,file="model.dat") # simple save R command
> # ...
> load("model.dat") # load the model from the previously saved file...
> model # should work but I get instead this error:
> Error in .jcall(x$classifier, "S", "toString") :
>  RcallMethod: attempt to call a method of a NULL object.
>
> What is wrong and how can I solve this problem?

The R object is just a reference to the corresponding object on the Java 
side (in Weka). When you close R, the Java/Weka session is also closed and 
the model is gone. Thus, when you load the object again in a new session, 
you only have a reference to a Java object that does not live anymore.
Z

> Regards,
> -- 
> Paulo Alexandre Ribeiro Cortez  (PhD, MSc)
> Lecturer (Prof. Auxiliar) at the Department of Information Systems (DSI)
> University of Minho, Campus de AzurÈm, 4800-058 Guimaraes, Portugal
> http://www.dsi.uminho.pt/~pcortez +351253510313 Fax:+351253510300
>
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