[R] rpart question on loss matrix

Peter Flom flom at ndri.org
Wed Jan 7 16:13:30 CET 2004

Hello again

I've looked through ?rpart, Atkinson & Therneau (1997), Chap 10 of
Venables and Ripley, Breman et al., and the r hgelp archives  but
haven't seen the answer to these two questions

1) How does rpart deal with asymmetric loss matrices?  Breiman et al.
suggest some possibilities, but, of course, do not say how rpart does

2) In the loss matrix, which direction (column or row) is 'truth' and
which 'output of program'?  e.g., if you have a 3 level DV (say the
levels are A, B, C) and you want a higher cost for misclassifying as
later in the alphabet, would it be

0  3  5  
1  0  2
2  1  0


0  1  2
3  0  1  
5  2  0

Thanks in advance


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