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1 function minima = som_dmatminima(sM,U,Ne)
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2
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3 %SOM_DMATMINIMA Find clusters based on local minima of U-matrix.
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4 %
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5 % minima = som_dmatminima(sM,[U],[Ne])
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6 %
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7 % Input and output arguments ([]'s are optional):
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8 % sM (struct) map struct
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9 % U (matrix) the distance matrix from which minima is
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10 % searched from
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11 % size msize(1) x ... x msize(end) or
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12 % 2*msize(1)-1 x 2*msize(2)-1 or
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13 % munits x 1
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14 % Ne (matrix) neighborhood connections matrix
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15 %
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16 % minima (vector) indeces of the map units where locla minima of
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17 % of U-matrix (or other distance matrix occured)
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18 %
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19 % See also KMEANS_CLUSTERS, SOM_CLLINKAGE, SOM_CLSTRUCT.
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20
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21 % Copyright (c) 2000 by Juha Vesanto
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22 % Contributed to SOM Toolbox on June 16th, 2000 by Juha Vesanto
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23 % http://www.cis.hut.fi/projects/somtoolbox/
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24
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25 % Version 2.0beta juuso 220800
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26
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27 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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28
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29 % map
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30 if isstruct(sM),
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31 switch sM.type,
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32 case 'som_map', M = sM.codebook; mask = sM.mask;
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33 case 'som_data', M = sM.data; mask = ones(size(M,2),1);
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34 end
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35 else
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36 M = sM; mask = ones(size(M,2),1);
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37 end
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38 [munits dim] = size(M);
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39
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40 % distances between map units
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41 if nargin<2, U = []; end
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42
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43 % neighborhoods
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44 if nargin<3, Ne = som_neighbors(sM); end
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45
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46 % distance matrix
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47 if nargin<2 | isempty(U), U = som_dmat(sM,Ne,'median'); end
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48 if prod(size(U))>munits, U = U(1:2:size(U,1),1:2:size(U,2)); end
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49 U = U(:);
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50 if length(U) ~= munits, error('Distance matrix has incorrect size.'); end
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51
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52 % find local minima
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53 minima = [];
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54 for i=1:munits,
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55 ne = find(Ne(i,:));
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56 if all(U(i)<=U(ne)) & ~anycommon(ne,minima), minima(end+1)=i; end
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57 end
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58
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59 return;
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60
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61 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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62
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63 function t = anycommon(i1,i2)
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64 if isempty(i1) | isempty(i2), t = 0;
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65 else
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66 m = max(max(i1),max(i2));
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67 t = any(sparse(i1,1,1,m,1) & sparse(i2,1,1,m,1));
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68 end
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69 return;
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70
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