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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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