Surrogate splits for decision trees

Dear R,

Short verse of the question:

Is there R code which will calculate surrogate splits
and/or delta impurity for decision trees at each node?


Long Version:

I have local, legacy code which I use to calculate my decision trees.
I would like to switch to R, but as I understand it surrogate splits
are not implemented.

Surrogate splits and feature ranking are described in Breiman et al
"CART" 1984.  Curiously, they don't seem to appear anywhere else
in the literature.

Can anyone comment on how extenible Ripley's tree package is?

Thanks in advance,


--Clayton

Clayton Springer, Ph. D.
Sandia National Laboratories                      csprin at ca.sandia.gov
Biosystems Research Department                    (925) 294-2143
P.O. Box 969, MS 9951                fax:         (925) 294-3020
Livermore, CA, 94551-0969

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