minsplit
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the minimum number of observations that must exist in a node, in order for
a split to be attempted.
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minbucket
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the minimum number of observations in any terminal <leaf> node.
If only one of minbucket or minsplit is specified, the code either sets
minsplit to minbucket*3 or minbucket to minsplit/3 , as appropriate.
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cp
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complexity parameter. Any split that does not decrease the overall lack of
fit by a factor of cp is not attempted. For instance, with anova splitting,
this means that the overall Rsquare must increase by cp at each step.
The main role of this parameter is to save computing time by pruning off
splits that are obviously not worthwhile.
Essentially,the user informs the program that any split which does not improve
the fit by cp will likely be pruned off by cross-validation, and that hence
the program need not pursue it.
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maxcompete
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the number of competitor splits retained in the output. It is useful to
know not just which split was chosen, but which variable came in second,
third, etc.
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maxsurrogate
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the number of surrogate splits retained in the output. If this is set to
zero the compute time will be shortened, since approximately half of the
computational time (other than setup) is used in the search for surrogate
splits.
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usesurrogate
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how to use surrogates in the splitting process. 0= display only; an
observation with a missing value for the primary split rule is not sent
further down the tree. 1= use surrogates, in order, to split subjects
missing the primary variable; if all surrogates are missing the observation
is not split. 2= if all surrogates are missing, then send the observation
in the majority direction. A value of 0 corresponds to the action of tree ,
and 2 to the recommendations of Breiman, et.al.
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xval
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number of cross-validations
|