###

PDF type

Each combination of signal class and feature set must be
accompanied by a PDF estimator (See section 14.3.1).
We need to define which PDF type is used to estimate these.
We have defined two types `gauss` and `gmm`,
Gaussian and Gaussian mixtire, respectively.
An arbitrary PDF type can be user-defined,
pdf_type='xxx';
OR:
pdf_type='xxx_yyy';

but the function `pdf_xxx.m` must exist
(use `software/pdf_gauss.m` or `software/pdf_gmm.m` as templates).
If the suffix `_yyy` or `_yyy_zzz`, etc, is added to the `pdf_type` variable,
the character string , `'yyy'` or `yyy_zzz` will be passed to the function
`pdf_xxx.m` as input variable `pstr`. To see how this works,
look at `software/pdf_gmm.m`. The parameter `'yyy'` defines the number of
mixture components, for example
pdf_type='gmm_2';

specifies a Gaussian mixture with two mixture components.

Baggenstoss
2017-05-19