D: binary tree method
Binary tree classifiers divide a complex problem into several simple
ones and then tackle the sub-problem. If the separated classes
include plural classes at the node connected to the top node, the
hyperplane that separates the classes should be obtained. It repeats
until only one class remains in the separated region. Finally,
the original multi-class is divided into many two class nodes. Fig. 2
shows two representative trees for the SVM. One is slant binary
tree SVM (SBTSVM), and the other is balanced binary tree SVM
(BBTSVM). At each node one class is separated from the remaining
classes for SBTSVM. But some classes are separated from the
remaining classes at each node for BBTSVM. The top of the tree includes
all the original classes. Each internal node consists of either
a set of class pairs or a single class.