Graphics Reference
In-Depth Information
Figure
.
.
Trace plot of
bootstrapped trees
Conclusion
10.4
Tree models are very rich and versatile. Equally rich is the variety of possible visu-
alization techniques that provide various views of trees, each time shedding light on
different properties of the models.
Hierarchical views are the most commonly used graphical representations and
highlight the sequence of splits. hey are easy to interpret even by untrained per-
sonnel. Node placement and representation can convey additional information as-
sociated with the model or data. Size of nodes can be intuitively associated with the
size of the data passed into that node. Highlighting and brushing is easily possible in
this context, whichfacilitates interpretation in conjunction with available data. Hier-
archical views oten allow for additional annotation and supplemental information,
such as split quality. Complemental methods are available for large trees and data,
such as censored or context-preserving local zoom.
A less known group of tree model visualization techniques are those based on the
recursive partitioning aspect. Direct viewof the partition boundaries in the observa-
tion space can be obtained using sectioned scatterplots.hefocushereliesonthecut
points and their relative position in the data space. hey are limited in terms of the
number andtypes ofcovariates usedbutprove tobe usefulas adrill-down technique
for local analysis of subgroups throughout the tree model.
