comparison DL/two-step DL/dico_decorr_symetric.m @ 220:0d30f9074dd9

Merge
author luisf <luis.figueira@eecs.qmul.ac.uk>
date Wed, 11 Apr 2012 15:56:39 +0100
parents 69ce11724b1f
children fd0b5d36f6ad
comparison
equal deleted inserted replaced
165:775caafd5651 220:0d30f9074dd9
1 function dico = dico_decorr_symetric(dico, mu)
2 %DICO_DECORR decorrelate a dictionary
3 % Parameters:
4 % dico: the dictionary, either a matrix or a cell array of matrices.
5 % mu: the coherence threshold
6 %
7 % Result:
8 % dico: if the input dico was a matrix, then a matrix close to the
9 % input one with coherence mu.
10 % If the input was a cell array, a cell array of the same size
11 % containing matrices such that the coherence between different cells
12 % is lower than mu.
13
14 eps = 1e-3; % define tolerance for normalisation term alpha
15
16 % convert mu to the to the mean direction
17 theta = acos(mu)/2;
18 ctheta = cos(theta);
19 stheta = sin(theta);
20
21 % compute atom weights
22 % if nargin > 2
23 % rank = sum(amp.*amp, 2);
24 % else
25 % rank = randperm(length(dico));
26 % end
27
28 % if only one dictionary is provided, then decorrelate it
29 if ~iscell(dico)
30 % several decorrelation iterations might be needed to reach global
31 % coherence mu. niter can be adjusted to needs.
32 niter = 1;
33 while max(max(abs(dico'*dico -eye(length(dico))))) > mu + eps
34 % find pairs of high correlation atoms
35 colors = dico_color(dico, mu);
36
37 % iterate on all pairs
38 nbColors = max(colors);
39 for c = 1:nbColors
40 index = find(colors==c);
41 if numel(index) == 2
42 if dico(:,index(1))'*dico(:,index(2)) > 0
43 %build the basis vectors
44 v1 = dico(:,index(1))+dico(:,index(2));
45 v1 = v1/norm(v1);
46 v2 = dico(:,index(1))-dico(:,index(2));
47 v2 = v2/norm(v2);
48
49 dico(:,index(1)) = ctheta*v1+stheta*v2;
50 dico(:,index(2)) = ctheta*v1-stheta*v2;
51 else
52 v1 = dico(:,index(1))-dico(:,index(2));
53 v1 = v1/norm(v1);
54 v2 = dico(:,index(1))+dico(:,index(2));
55 v2 = v2/norm(v2);
56
57 dico(:,index(1)) = ctheta*v1+stheta*v2;
58 dico(:,index(2)) = -ctheta*v1+stheta*v2;
59 end
60 end
61 end
62 niter = niter+1;
63 end
64 %if a cell array of dictionaries is provided, decorrelate among
65 %different dictionaries only
66 else
67 niter = 1;
68 numDicos = length(dico);
69 G = cell(numDicos);
70 maxCorr = 0;
71 for i = 1:numDicos
72 for j = i+1:numDicos
73 G{i,j} = dico{i}'*dico{j};
74 maxCorr = max(maxCorr,max(max(abs(G{i,j}))));
75 end
76 end
77
78 while maxCorr > mu + eps
79 % find pairs of high correlation atoms
80 [colors nbColors] = dico_color_separate(dico, mu);
81
82 % iterate on all pairs
83 for c = 1:nbColors
84 for tmpI = 1:numDicos
85 index = find(colors{tmpI}==c);
86 if ~isempty(index)
87 i = tmpI;
88 m = index;
89 break;
90 end
91 end
92 for tmpJ = i+1:numDicos
93 index = find(colors{tmpJ}==c);
94 if ~isempty(index)
95 j = tmpJ;
96 n = index;
97 break;
98 end
99 end
100
101 if dico{i}(:,m)'*dico{j}(:,n) > 0
102 %build the basis vectors
103 v1 = dico{i}(:,m)+dico{j}(:,n);
104 v1 = v1/norm(v1);
105 v2 = dico{i}(:,m)-dico{j}(:,n);
106 v2 = v2/norm(v2);
107
108 dico{i}(:,m) = ctheta*v1+stheta*v2;
109 dico{j}(:,n) = ctheta*v1-stheta*v2;
110 else
111 v1 = dico{i}(:,m)-dico{j}(:,n);
112 v1 = v1/norm(v1);
113 v2 = dico{i}(:,m)+dico{j}(:,n);
114 v2 = v2/norm(v2);
115
116 dico{i}(:,m) = ctheta*v1+stheta*v2;
117 dico{j}(:,n) = -ctheta*v1+stheta*v2;
118 end
119 end
120 niter = niter+1;
121
122 % Remove noegative components and renormalize
123 for i = 1:length(dico)
124 dico{i} = max(dico{i},0);
125 for m = 1:size(dico{i},2)
126 dico{i}(:,m) = dico{i}(:,m)/norm(dico{i}(:,m));
127 end
128 end
129
130 maxCorr = 0;
131 for i = 1:numDicos
132 for j = i+1:numDicos
133 G{i,j} = dico{i}'*dico{j};
134 maxCorr = max(maxCorr,max(max(abs(G{i,j}))));
135 end
136 end
137 end
138 end
139 end