88 lines
2.2 KiB
Mathematica
88 lines
2.2 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,variabletype] = 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 all(variabletype(x_lin) ==0)% 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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variabletype = variabletype(x_lin);
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if all(variabletype<=2)
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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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quads = find (variabletype == 2);
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bilins = find (variabletype == 1);
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linears = find (variabletype == 0);
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[varsC,aux1,aux2] = find(mt(linears,:)');
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[varsQ,aux1,aux2] = find(mt(quads,:)');
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[varsB,aux1,aux2] = find(mt(bilins,:)');
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if isempty(varsQ)
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varsQ = [];
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end
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if isempty(varsB)
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varsB = [];
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end
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if isempty(varsC)
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varsC = [];
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end
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c = sparse(varsC,1,base(linears),length(x),1);
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ii = [varsQ ; varsB(1:2:end) ; varsB(2:2:end)];
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jj = [varsQ ; varsB(2:2:end) ; varsB(1:2:end)];
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kk = [base(quads) base(bilins)/2 base(bilins)/2];
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Q = sparse(ii,jj,kk,length(x),length(x));
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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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