Rev | Line | |
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[37] | 1 | function d = det(X) |
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| 2 | %DET (overloaded) |
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| 3 | |
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| 4 | % Author Johan Löfberg |
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| 5 | % $Id: det.m,v 1.4 2006/07/26 20:17:57 joloef Exp $ |
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| 6 | |
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| 7 | n = X.dim(1); |
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| 8 | m = X.dim(2); |
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| 9 | |
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| 10 | if n~=m |
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| 11 | error('Matrix must be square.'); |
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| 12 | else |
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| 13 | switch n |
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| 14 | case 1 |
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| 15 | d = X; |
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| 16 | case 2 |
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| 17 | % Freakin overloading on multiplication doesn't work. Probalby |
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| 18 | % stupid code... |
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| 19 | Y1.type = '()'; |
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| 20 | Y2.type = '()'; |
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| 21 | Y3.type = '()'; |
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| 22 | Y4.type = '()'; |
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| 23 | Y1.subs = {1,1}; |
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| 24 | Y2.subs = {2,2}; |
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| 25 | Y3.subs = {1,2}; |
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| 26 | Y4.subs = {2,1}; |
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| 27 | d = subsref(X,Y1)*subsref(X,Y2)-subsref(X,Y3)*subsref(X,Y4); |
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| 28 | otherwise |
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| 29 | d = 0; |
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| 30 | Y.type = '()'; |
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| 31 | for i = 1:n |
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| 32 | Y.subs = {i,1}; |
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| 33 | xi = subsref(X,Y); |
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| 34 | if ~isequal(xi,0) |
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| 35 | Y.subs = {[1:1:i-1 i+1:1:n],2:n}; |
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| 36 | subX = subsref(X,Y); |
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| 37 | d = d + (-1)^(i+1)*xi*det(subX); |
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| 38 | end |
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| 39 | end |
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| 40 | end |
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| 41 | end |
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| 42 | % Reset info about conic terms |
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| 43 | d.conicinfo = [0 0]; |
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