We now consider the general linear transformations
of spectral or intensity data, which is widely used
in signal and image processing and spectral analysis.
The most widely-used application of this feature is in spectral
and intensity image classification and analysis.
An example is the calculation of the band energies
as an initial stage in the calculation of MFCC coefficients.
Despite the simplicity of the feature transformation,
the positive-valued input data makes the problem
more challenging and requires
a chapter on its own.
Linear transformation of positive data