Statistics Toolbox™

classprob - Class probabilities

Class

@classregtree

Syntax

P = classprob(t) P = classprob(t,nodes)

Description

P = classprob(t) returns an n-by-m array P of class probabilities for the nodes in the classification tree t, where n is the number of nodes and m is the number of classes. For any node number i, the class probabilities P(i,:) are the estimated probabilities for each class for a point satisfying the conditions for node i.

P = classprob(t,nodes) takes a vector nodes of node numbers and returns the class probabilities for the specified nodes.

Example

Create a classification tree for Fisher's iris data:

load fisheriris;

t = classregtree(meas,species,...
                 'names',{'SL' 'SW' 'PL' 'PW'})
t = 
Decision tree for classification
1  if PL<2.45 then node 2 else node 3
2  class = setosa
3  if PW<1.75 then node 4 else node 5
4  if PL<4.95 then node 6 else node 7
5  class = virginica
6  if PW<1.65 then node 8 else node 9
7  class = virginica
8  class = versicolor
9  class = virginica

view(t)

P = classprob(t)
P =
    0.3333    0.3333    0.3333
    1.0000         0         0
         0    0.5000    0.5000
         0    0.9074    0.0926
         0    0.0217    0.9783
         0    0.9792    0.0208
         0    0.3333    0.6667
         0    1.0000         0
         0         0    1.0000

Reference