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