R help - May 2009 - Rpart - best split selection for class method and Gini splitting index

Dear R-users,
I'm working with the Rpart package and trying to understand how the 
procedure select the best split in the case the method "class" and the
splitting index "Gini" are used. In particular I'd like to have
look to the
source code that works out the best split for un unordered predictor.
Does anyone can suggest me which functions in the sources I should consider 
?
Any input would be highly appreciated.

Thank you
Paolo

Paolo Radaelli
Dipartimento di Metodi Quantitativi per le Scienze Economiche ed Aziendali
Facolt? di Economia
Universit? degli Studi di Milano-Bicocca
Via Bicocca degli Arcimboldi, 8
20126 Milano
Italy
e-mail paolo.radaelli at unimib.it
Tel +39 02 6448 3163
Fax +39 02 6448 3105

On Thu, 21 May 2009, Paolo Radaelli wrote:
>
> Dear R-users,
> I'm working with the Rpart package and trying to understand how the
procedure
I presume you mean 'rpart': R package names are case sensitive.
> select the best split in the case the method "class" and the 
> splitting index "Gini" are used. In particular I'd like to
have look
> to the source code that works out the best split for un unordered 
> predictor.
> Does anyone can suggest me which functions in the sources I should 
> consider ?
It done in C.  Start with file bsplit.c, that says

** The routine which will find the best split for a node

Then look at gini.c (again, pretty obvious, I believe).
> Any input would be highly appreciated.
>
> Thank you
> Paolo
>
> Paolo Radaelli
> Dipartimento di Metodi Quantitativi per le Scienze Economiche ed Aziendali
> Facolt? di Economia
> Universit? degli Studi di Milano-Bicocca
> Via Bicocca degli Arcimboldi, 8
> 20126 Milano
> Italy
> e-mail paolo.radaelli at unimib.it
> Tel +39 02 6448 3163
> Fax +39 02 6448 3105
>
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>
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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