www.pudn.com > ConstrainedEM.zip > best_params_using_chunklets.m

function [bestParam] =best_params_using_chunklets(data,chunklets,M,... 
    singleCovMatFlag,diag_covmat_flag,priorFlag,number_of_starts) 
 
% this function finds start conditions for the mixture parameters. 
% if chunklets are given , they are used in the process. 
% currently only single covmat is supported. 
 
%priorFlag  - if 1 will use smoothing in RCA cov estimation. default 
%is zero 
if(~exist('number_of_starts')) 
    number_of_starts=30; 
end 
 
if(~exist('priorFlag')) 
  priorFlag=0; 
end 
 
if(~exist('diag_covmat_flag')) 
  diag_covmat_flag=0; 
end 
 
% M -the number of models 
[ n , dim ]=size(data); 
 
bestParam=cell(M,3); 
 
% wishart prior option :	% this is a prior on the covmat assessed by RCA. the prior 
% is used if the flag is on. 
% according to 'priors on dag models' of Heckerman and Geiger, p. 10 
 
wishart_prior_flag=1;	 
T=eye(dim);		% the prior covmat. 
alpha=n/20;		% the prior 'virtual sample' size. 
 
 
if singleCovMatFlag 
   % the model weights are equiprobable 
   for i=1:M 
        bestParam{i,3}=1/M;  % uniform weights 
    end 
    
   % do RCA for the covmat 
 
   [WhitenedData, bestParam{1,2} ]= RCAwhitenChunklets(chunklets,data',priorFlag); 
   if wishart_prior_flag==1 
      m=length(find(chunklets~=-1)); 
      Sm=bestParam{1,2}*m; 
      bestParam{1,2}=(alpha*T+Sm)/(m+alpha);	% is this the map for a wishart distribution? 
						% it needs to be determnied. 
   end 
                                           
   if(diag_covmat_flag) 
     bestParam{1,2}= bestParam{1,2}.*T; 
   end 
    
   % find centers 
    
    bll=-inf;       % best log liklihood. 
   i=1; 
   infFlag= 1; 
   noiseParam=[2 5 10];	 % alters the number of neighbors to be used for 
   % choosing centers. when large, the number of  neighobrs used for 
   % centroid computation is smaller. 
   while (i <= number_of_starts)  
      param = select_start_params(data,bestParam,singleCovMatFlag,1,M,dim,n,noiseParam(ceil(i/10)),chunklets);  
      [p , ll ]=calc_p_and_ll(data,param,singleCovMatFlag); 
      if ll>=bll 
         bll=ll; 
         bestParam=param; 
      end 
      i= i+1; 
      if(bll ~= -inf) 
         infFlag=0; 
      end 
   end 
   if infFlag==1 
      bestParam=[]; 
   end 
else  
   ' ou est le chien ? ' 
end