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', 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: 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 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, '+1' if it
          goes to the right, and 0 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'.

