108 lines
2.7 KiB
Mathematica
108 lines
2.7 KiB
Mathematica
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function [Q,c,f,x,info] = quaddecomp(p,z)
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%QUADDECOMP Internal function to decompose quadratic expression
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[n,m]=size(p);
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info = 0;
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% Is it a scalar
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if (n*m==1)
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% Involved in polynomial expression
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mt = yalmip('monomtable');
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x_lin = getvariables(p);
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x_var = find(any(mt(x_lin,:),1));
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if nargin==2
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x_var = union(x_var,depends(z));
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end
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x = recover(x_var);
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if is(p,'linear')
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n = length(x);
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Q = spalloc(n,n,0);
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fc = getbase(p);
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f = fc(1);
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if nargin==2
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vars = getvariables(p);
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c = zeros(length(x),1);
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for i = 1:length(vars)
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c(find(vars(i)==x_var)) = fc(1+i);
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end
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else
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c = fc(2:end);c=c(:);
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end
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return
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end
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degrees = sum(mt(x_lin,:),2);
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if all(degrees<=2)
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Q = spalloc(length(x),length(x),2*nnz(getbase(p)));
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c = zeros(length(x),1);
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base = getbase(p);
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if nnz(base(1))==0
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f = 0;
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base = base(2:end);
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else
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f = base(1);
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base = base(2:end);
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end
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mt = mt(x_lin,x_var);
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if 1
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[jj,ii,kk] = find(mt');ii = [ii(:) ;0];
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top = 1;
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for i = 1:length(x_lin)
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if ii(top) == ii(top+1)
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j = [jj(top) jj(top+1)];
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top = top + 2;
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else
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j = [jj(top)];
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top = top + 1;
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end
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if length(j)==1 % One variable
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if kk(top-1)==1
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c(j)=base(i);
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else
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Q(j,j)=Q(j,j) + base(i)/2;
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end
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else
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Q(j(1),j(2))=Q(j(1),j(2)) + base(i)/2;
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end
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end
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else
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for i = 1:length(x_lin)
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j = find(mt(i,:)); % What variables are used
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if length(j)==1 % One variable
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if mt(i,j)==1
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c(j)=base(i);
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else
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Q(j,j)=Q(j,j) + base(i)/2;
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end
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else
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Q(j(1),j(2))=Q(j(1),j(2)) + base(i)/2;
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end
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end
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end
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Q = Q+Q';
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else
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if nargout==5
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info = 1;
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Q = [];
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c = [];
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f = [];
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x = [];
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else
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error('Function is not quadratic');
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end
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end
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else
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if nargout==5
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info = 1;
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Q = [];
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c = [];
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f = [];
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x = [];
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else
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error('Function is not scalar');
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end
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end
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