52 lines
1.5 KiB
Mathematica
52 lines
1.5 KiB
Mathematica
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function varargout=nchoosek(varargin)
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%NCHOOSEK (overloaded)
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switch class(varargin{1})
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case 'double'
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error('Overloaded SDPVAR/NCHOOSEK CALLED WITH DOUBLE. Report error')
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case 'sdpvar' % Overloaded operator for SDPVAR objects. Pass on args and save them.
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if nargin ~=2
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error('Expecting two arguments')
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end
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n = varargin{1};
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k = varargin{2};
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if isa(k,'sdpvar')
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error('SDPVAR/NCHOOSEK currently only supported for fixed k');
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end
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varargout{1} = InstantiateElementWise(mfilename,varargin{:});
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case 'char' % YALMIP send 'graph' when it wants the epigraph or hypograph
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t = varargin{2};
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n = varargin{3};
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k = varargin{4};
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[U,L] = derivebounds(n);
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if isinf(U) | isinf(L)
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error('Bounds required on variables in nhoosek');
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end
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L = ceil(L);
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U = floor(U);
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range = L:U;
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for i = range
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if i>=k
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nchoosekVal(i) = nchoosek(i,k);
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else
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nchoosekVal(i) = 0;
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end
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end
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nchoosekVal = nchoosekVal(L:U);
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z = binvar(length(range),1);
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F = [n == range*z, t == nchoosekVal*z,sum(z)==1];
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varargout{1} = F;
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varargout{2} = struct('convexity','none','monotonicity','increasing','definiteness','positive','model','integer');
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varargout{3} = n;
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otherwise
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error('Strange type on first argument in SDPVAR/SORT');
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end
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