rpart
Hi, I think most, if not all, your questions can be answered by: 1) ?rpart 2) Some search through the r-help mailing list 3) Read the chapter on tree-based models in MASS 4 (Modern Applied Statistics with S) by Venables and Ripley Kevin ----- Original Message ----- From: <h0444k87 at student.hu-berlin.de> To: <r-help at stat.math.ethz.ch> Sent: Friday, June 04, 2004 9:59 PM Subject: [R] rpart
Hello everyone, I'm a newbie to R and to CART so I hope my questions don't seem too
stupid.
1.) My first question concerns the rpart() method. Which method does rpart use
in
order to get the best split - entropy impurity, Bayes error (min. error)
or Gini
index? Is there a way to make it use the entropy impurity? The second and third question concern the output of the printcp()
function.
2.) What exactly are the cps in that sense here? I assumed them to be the
treshold
complexity parameters as in Breiman et al., 1998, Section 3.3? Are they
the same
as the treshold niveaus of alpha? I have read somewhere that the cps here
are
the treshold alphas divided by the root node error. Is that true? 3.) How is rel error computed? I am supposed to evaluate the goodness of classification of of the CART
method.
Do you think rel error is a good measure for that? I'd be very thankful if anyone could give me hand on that. This is a
project for
uni and I desperately need a good mark. Thank you very much in advance, Mareike
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