rpart.object              package:rpart              R Documentation

Recursive Partitioning and Regression Trees Object

Description:

     These are objects representing fitted 'rpart' trees.

Value:

   frame: data frame with one row for each node in the tree. The
          'row.names' of 'frame' contain the (unique) node numbers that
          follow a binary ordering indexed by node depth. Elements of
          'frame' include 'var', a factor giving the variable used in
          the split at each node (leaf nodes are denoted by the string
          '<leaf>'), 'n', the size of each node, 'wt', the sum of case
          weights for the node, 'dev', the deviance of each node,
          'yval', the fitted value of the response at each node, and
          'splits', a two column matrix of left and right split labels
          for each node. All of these are the same as for an 'rpart'
          object.

          Extra response information is in 'yval2', which contains the
          number of events at the node (poisson), or a matrix
          containing the fitted class, the class counts for each node
          and the class probabilities (classification).  Also included
          in the frame are 'complexity', the complexity parameter at
          which this split will collapse, 'ncompete', the number of
          competitor splits retained, and 'nsurrogate', the number of
          surrogate splits retained. 

   where: integer vector, the same length as the number of observations
          in the root node,  containing the row number of 'frame'
          corresponding to the leaf node  that each observation falls
          into.  

  splits: a numeric matrix describing the splits.  The row label is the
          name of the split variable, and columns are 'count', the
          number of observations sent left or right by the split (for
          competitor splits this is the number that would have been
          sent left or right had this split been used, for surrogate
          splits it is the number missing the primary split variable
          which were decided using this surrogate), 'ncat', the number
          of categories or levels for the variable ('+/-1' for a
          continuous variable), 'improve', which is the improvement in
          deviance given by this split, or, for surrogates, the
          concordance of the surrogate with the primary, and 'split',
          the numeric split point.   The last column 'adj' gives the
          adjusted concordance for surrogate splits. For a factor, the
          'split' column contains the row number of the csplit matrix.
          For a continuous variable, the sign of 'ncat' determines
          whether the subset 'x < cutpoint' or 'x > cutpoint' is sent
          to the left. 

  csplit: this will be present only if one of the split variables is a
          factor. There is one row for each such split, and column 'i =
          1' if this level of the factor goes to the left, '3' if it
          goes to the right, and 2 if that level is not present at this
          node of the tree. For an ordered categorical variable all
          levels are marked as 'R/L',  including levels that are not
          present. 

  method: the method used to grow the tree.  

 cptable: the table of optimal prunings based on a complexity
          parameter.  

   terms: an object of mode 'expression' and class 'term' summarizing
          the formula.  Used by various methods, but typically not of
          direct relevance to users.  

    call: an image of the call that produced the object, but with the
          arguments  all named and with the actual formula included as
          the formula argument.  To re-evaluate the call, say
          'update(tree)'. 

          Optional components include the matrix of predictors ('x')
          and the  response variable ('y') used to construct the
          'rpart' object.  

Structure:

     The following components must be included in a legitimate 'rpart'
     object.  Of these, only the 'where' component has the same length
     as   the data used to fit the 'rpart' object.

See Also:

     'rpart'.

