[R] rpart

[henrigel at gmx.de]

Dear r-help-list:

If I use the rpart method like

cfit<-rpart(y~.,data=data,...),

what kind of tree is stored in cfit?
Is it right that this tree is not pruned at all, that it is the full tree?

If so, it's up to me to choose a subtree by using the printcp method.
In the technical report from Atkinson and Therneau "An Introduction to recursive partitioning using the rpart routines" from 2000, one can see the following table on page 15:

      CP  nsplit  relerror  xerror   xstd
1   0.105   0     1.00000   1.0000   0.108
2   0.056   3     0.68519   1.1852   0.111
3   0.028   4     0.62963   1.0556   0.109
4   0.574   6     0.57407   1.0556   0.109
5   0.100   7     0.55556   1.0556   0.109

Some lines below it says "We see that the best tree has 5 terminal nodes (4 splits). Why that if the xerror is the lowest for the tree only consisting of the root?

Thank you very much for your help

Henri 
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