1 | function Y=diff(varargin) |
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2 | %DIFF (overloaded) |
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3 | |
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4 | % Author Johan Löfberg |
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5 | % $Id: diff.m,v 1.6 2006/07/26 20:17:57 joloef Exp $ |
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6 | |
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7 | X = varargin{1}; |
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8 | n = X.dim(1); |
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9 | m = X.dim(2); |
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10 | |
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11 | Y = X; |
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12 | x_lmi_variables = X.lmi_variables; |
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13 | lmi_variables = []; |
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14 | |
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15 | % Fast diff of large matrices. Convert to optmized case |
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16 | switch nargin |
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17 | case 1 |
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18 | if (min([n m]) > 1) |
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19 | Y = diff(X',1,2)'; |
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20 | return |
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21 | end |
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22 | |
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23 | case 2 |
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24 | if varargin{2} == 1 & (min([n m]) > 1) |
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25 | Y = diff(X',1,2)'; |
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26 | return |
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27 | end |
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28 | case 3 |
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29 | if varargin{2}==1 & varargin{3} == 2 & (min([n m]) > 1) |
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30 | shift = [-speye(m-1) spalloc(m-1,1,0)] + [spalloc(m-1,1,0) speye(m-1)]; |
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31 | % shift = shift(1:m-1,1:m); |
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32 | shift = kron(shift,speye(n)); |
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33 | Y.basis = shift*X.basis; |
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34 | Y.dim(1) = n; |
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35 | Y.dim(2) = m - 1; |
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36 | % Reset info about conic terms |
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37 | Y.conicinfo = [0 0]; |
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38 | Y = clean(Y); |
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39 | return |
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40 | elseif varargin{2}==1 & varargin{3} == 1 & (min([n m]) > 1) |
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41 | Y = diff(X',1,2)'; |
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42 | return |
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43 | end |
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44 | |
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45 | otherwise |
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46 | error('To many input arguments.') |
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47 | end |
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48 | |
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49 | % Slow but safe case. Used for higher order diff |
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50 | try |
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51 | j = 1; |
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52 | diffX = diff(reshape(X.basis(:,1),n,m),varargin{2:end}); |
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53 | Y.basis=diffX(:); |
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54 | for i = 1:length(x_lmi_variables) |
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55 | diffX = diff(reshape(X.basis(:,i+1),n,m),varargin{2:end}); |
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56 | if (norm(diffX,inf)>0) |
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57 | Y.basis(:,j+1) = diffX(:); |
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58 | lmi_variables = [lmi_variables x_lmi_variables(i)]; |
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59 | j = j+1; |
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60 | end |
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61 | end |
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62 | if j~=1 |
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63 | Y.lmi_variables = lmi_variables; |
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64 | else |
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65 | Y = full(reshape(Y.basis(:,1),size(diffX,1),size(diffX,2))); |
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66 | return |
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67 | end |
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68 | catch |
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69 | error(lasterr) |
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70 | end |
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71 | Y.dim(1) = size(diffX,1); |
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72 | Y.dim(2) = size(diffX,2); |
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73 | % Reset info about conic terms |
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74 | Y.conicinfo = [0 0]; |
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