
of LDA features is 1 less than the number of classes. This is because S
b
is of rank
c 1 or less. Also, since the rank of S
w
is at most M c, M must be greater than
or equal to L þ c in order to ensure that S
w
does not become singular.
In summary, since LDA maximizes the ability of the new features to
discriminate among the classes, it is generally considered to be more effective
than PCA for feature reduction prior to classification.
11.11 Neural Networks
A completely different approach to classification is the use of artificial neural
networks (ANNs) [5]. Here a network is composed of one or more layers of
interconnected processing elements (PEs). Each ...