wolffd@0: function Ne = som_neighbors(sM,neigh)
wolffd@0: 
wolffd@0: % Ne = som_neighbors(sM,neigh)
wolffd@0: %
wolffd@0: % sM      (struct) map or data struct
wolffd@0: %         (matrix) data matrix, size n x dim
wolffd@0: % [neigh] (string) 'kNN' or 'Nk' (which is valid for a SOM only)
wolffd@0: %                  for example '6NN' or 'N1'
wolffd@0: %                  default is '10NN' for a data set and 'N1' for SOM
wolffd@0: %
wolffd@0: % Ne      (matrix) size n x n, a sparse matrix
wolffd@0: %                  indicating the neighbors of each sample by value 1 
wolffd@0: %                  (note: the unit itself also has value 0)
wolffd@0: 
wolffd@0: %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
wolffd@0: 
wolffd@0: if isstruct(sM), 
wolffd@0:   switch sM.type, 
wolffd@0:    case 'som_map',  M = sM.codebook; 
wolffd@0:    case 'som_data', M = sM.data; sM = []; 
wolffd@0:   end
wolffd@0: else
wolffd@0:   M = sM; 
wolffd@0:   sM = []; 
wolffd@0: end
wolffd@0: 
wolffd@0: n = size(M,1);
wolffd@0: 
wolffd@0: if nargin<2, 
wolffd@0:   if isempty(sM), neigh = '10NN'; else neigh = 'N1'; end
wolffd@0: end
wolffd@0: 
wolffd@0: if strcmp(neigh(end-1:end),'NN'),
wolffd@0:   k  = str2num(neigh(1:end-2));
wolffd@0:   kmus = som_bmus(M,M,1:k+1);
wolffd@0:   Ne = sparse(n,n);
wolffd@0:   for i=1:n, Ne(i,kmus(i,:)) = 1; end
wolffd@0: else
wolffd@0:   if ~isstruct(sM), error('Prototypes must be in a map struct.'); end      
wolffd@0:   k  = str2num(neigh(2:end));
wolffd@0:   N1 = som_unit_neighs(sM);    
wolffd@0:   Ne = sparse(som_neighborhood(N1,k)<=k);
wolffd@0: end
wolffd@0: Ne([0:n-1]*n+[1:n]) = 0; % remove self from neighbors
wolffd@0: 
wolffd@0: return;