wolffd@0: function minima = som_dmatminima(sM,U,Ne)
wolffd@0: 
wolffd@0: %SOM_DMATMINIMA Find clusters based on local minima of U-matrix.
wolffd@0: %
wolffd@0: % minima = som_dmatminima(sM,[U],[Ne])
wolffd@0: %
wolffd@0: %  Input and output arguments ([]'s are optional):
wolffd@0: %   sM         (struct) map struct
wolffd@0: %   U          (matrix) the distance matrix from which minima is
wolffd@0: %                       searched from 
wolffd@0: %                       size msize(1) x ... x msize(end) or 
wolffd@0: %                            2*msize(1)-1 x 2*msize(2)-1 or 
wolffd@0: %                            munits x 1
wolffd@0: %   Ne         (matrix) neighborhood connections matrix
wolffd@0: %
wolffd@0: %   minima     (vector) indeces of the map units where locla minima of
wolffd@0: %                       of U-matrix (or other distance matrix occured)
wolffd@0: %   
wolffd@0: % See also KMEANS_CLUSTERS, SOM_CLLINKAGE, SOM_CLSTRUCT.
wolffd@0: 
wolffd@0: % Copyright (c) 2000 by Juha Vesanto
wolffd@0: % Contributed to SOM Toolbox on June 16th, 2000 by Juha Vesanto
wolffd@0: % http://www.cis.hut.fi/projects/somtoolbox/
wolffd@0:  
wolffd@0: % Version 2.0beta juuso 220800
wolffd@0: 
wolffd@0: %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
wolffd@0: 
wolffd@0: % map 
wolffd@0: if isstruct(sM), 
wolffd@0:   switch sM.type, 
wolffd@0:    case 'som_map',  M = sM.codebook; mask = sM.mask; 
wolffd@0:    case 'som_data', M = sM.data; mask = ones(size(M,2),1);
wolffd@0:   end
wolffd@0: else
wolffd@0:   M = sM; mask = ones(size(M,2),1);
wolffd@0: end
wolffd@0: [munits dim] = size(M);
wolffd@0: 
wolffd@0: % distances between map units
wolffd@0: if nargin<2, U = []; end
wolffd@0: 
wolffd@0: % neighborhoods 
wolffd@0: if nargin<3, Ne = som_neighbors(sM); end
wolffd@0: 
wolffd@0: % distance matrix
wolffd@0: if nargin<2 | isempty(U), U = som_dmat(sM,Ne,'median'); end
wolffd@0: if prod(size(U))>munits, U = U(1:2:size(U,1),1:2:size(U,2)); end
wolffd@0: U = U(:); 
wolffd@0: if length(U) ~= munits, error('Distance matrix has incorrect size.'); end
wolffd@0: 
wolffd@0: % find local minima
wolffd@0: minima = []; 
wolffd@0: for i=1:munits, 
wolffd@0:   ne = find(Ne(i,:));
wolffd@0:   if all(U(i)<=U(ne)) & ~anycommon(ne,minima), minima(end+1)=i; end
wolffd@0: end
wolffd@0: 
wolffd@0: return; 
wolffd@0: 
wolffd@0: %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
wolffd@0: 
wolffd@0: function t = anycommon(i1,i2)
wolffd@0:   if isempty(i1) | isempty(i2), t = 0; 
wolffd@0:   else 
wolffd@0:     m = max(max(i1),max(i2));
wolffd@0:     t = any(sparse(i1,1,1,m,1) & sparse(i2,1,1,m,1)); 
wolffd@0:   end
wolffd@0:   return;   
wolffd@0: