[37] | 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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