%PARZENDC Trainable classifier based on Parzen density estimation
%
% [W,H] = PARZENDC(A,H)
% [W,H] = A*PARZENDC([],H)
% [W,H] = A*PARZENDC(H)
%
% INPUT
% A Dataset
% H Smoothing parameters (optional; default: estimated from A for each class)
%
% OUTPUT
% W Trained Parzen classifier
% H Smoothing parameters, estimated from the data
%
% DESCRIPTION
% For each of the classes in the dataset A, a Parzen density is estimated
% using PARZENML. For each class, a feature normalisation on variance is
% included in the procedure. As a result, the Parzen density estimate uses
% different smoothing parameters for each class and each feature.
%
% If a set of smoothing parameters H is specified, no learning is performed,
% only the classifier W is produced. H should have the size of [C x K] if
% A has C classes and K features. If the size of H is [1 x K] or [C x 1],
% or [1 x 1], then identical values are assumed for all the classes and/or
% features.
%
% The densities for the points of a dataset B can be found by D = B*W.
% D is an [M x C] dataset, if B has M objects.
%
% EXAMPLES
% See PREX_DENSITY for densities and PREX_PARZEN for differences between
% PARZENC, PARZENDC and PARZENM.
%
%
% SEE ALSO (<a href="http://37steps.com/prtools">PRTools Guide</a>)
% DATASETS, MAPPINGS, PARZENC, PARZENM, PARZENML, PREX_DENSITY
% Copyright: R.P.W. Duin, r.p.w.duin@37steps.com
% Faculty EWI, Delft University of Technology
% P.O. Box 5031, 2600 GA Delft, The Netherlands
function [W,h] = parzendc(varargin)
mapname = 'ParzenD';
argin = shiftargin(varargin,'scalar');
argin = setdefaults(argin,[],[]);
if mapping_task(argin,'definition')
W = define_mapping(argin,'untrained',mapname);
elseif mapping_task(argin,'training') % Train a mapping.
[a,h] = deal(argin{:});
islabtype(a,'crisp','soft');
isvaldfile(a,2,2); % at least 2 objects per class, 2 classes
a = testdatasize(a);
a = testdatasize(a,'objects');
[m,k,c] = getsize(a);
nlab = getnlab(a);
if ~isempty(h) % Take user settings for smoothing parameters.
if size(h,1) == 1, h = repmat(h,c,1); end
if size(h,2) == 1, h = repmat(h,1,k); end
if any(size(h) ~= [c,k])
error('Array with smoothing parameters has a wrong size.');
end
else % Estimate smoothing parameters
% Scale A such that its mean is shifted to the origin and
% the variances of all features are scaled to 1.
ws = scalem(a,'variance');
b = a*ws;
% SCALE is basically [1/mean(A) 1/STD(A)] based on the properties of SCALEM.
scale = ws.data.rot;
if (size(scale,1) ~= 1) % formally ws.data.rot stores a rotation matrix
scale = diag(scale)'; % extract the diagonal if it does,
end % otherwise we already have it
h = zeros(c,k);
if islabtype(a,'crisp')
s = sprintf('parzendc: smoothing per class ');
prwaitbar(c,s);
for j=1:c
prwaitbar(c,j,[s int2str(j)]);
bb = seldat(b,j); % BB consists of the j-th class only.
h(j,:) = repmat(parzenml(bb),1,k)./scale;
end
prwaitbar(0);
elseif islabtype(a,'soft')
h = parzenml(a);
end
end
W = prmapping('parzen_map','trained',{a,h,getprior(a)},getlablist(a),k,c);
W = setname(W,mapname);
W = setcost(W,a);
end
return;