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[37] | 1 | function dist=distance(X,x); |
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| 2 | % dist=distance(X,x) |
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| 3 | % |
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| 4 | % computes the pairwise squared distance matrix between any column vectors in X and |
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| 5 | % in x |
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| 6 | % |
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| 7 | % INPUT: |
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| 8 | % |
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| 9 | % X dxN matrix consisting of N column vectors |
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| 10 | % x dxn matrix consisting of n column vectors |
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| 11 | % |
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| 12 | % OUTPUT: |
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| 13 | % |
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| 14 | % dist Nxn matrix |
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| 15 | % |
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| 16 | % Example: |
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| 17 | % Dist=distance(X,X); |
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| 18 | % is equivalent to |
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| 19 | % Dist=distance(X); |
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| 20 | % |
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| 21 | [D,N] = size(X); |
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| 22 | |
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| 23 | try |
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| 24 | if(nargin>=2) |
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| 25 | % PAIRWISE DISTANCES |
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| 26 | [D,n] = size(x); |
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| 27 | X2 = sum(X.^2,1); |
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| 28 | x2 = sum(x.^2,1); |
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| 29 | dotProd = X'*x; |
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| 30 | dist = repmat(x2,N,1)+repmat(X2',1,n)-2*dotProd; |
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| 31 | else |
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| 32 | [D,N] = size(X); |
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| 33 | if(exist('addv') & exist('addh')) |
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| 34 | X2 = sum(X.^2,1); |
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| 35 | dist=addh(addv(-2*X'*X,X2),X2); |
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| 36 | else |
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| 37 | X2 = repmat(sum(X.^2,1),N,1); |
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| 38 | dist = X2+X2'-2*X'*X; |
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| 39 | % fprintf('Please install addv and addh.\n'); |
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| 40 | end; |
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| 41 | end; |
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| 42 | |
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| 43 | catch |
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| 44 | dist=zeros(N); |
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| 45 | tic; |
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| 46 | fprintf('Not enough Memory\nComputing distance line by line ...\n'); |
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| 47 | for i=1:N-1 |
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| 48 | j=(i+1):N; |
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| 49 | dist(i,j)= ones(1,length(j)).*sum(X(:,i).^2)+sum(X(:,j).^2)-2.*(X(:,j)'*X(:,i))'; |
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| 50 | dist(j,i)=dist(i,j)'; |
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| 51 | end; |
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| 52 | fprintf('\n'); |
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| 53 | end; |
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| 54 | |
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