65 lines
2.1 KiB
Mathematica
65 lines
2.1 KiB
Mathematica
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function varargout=find(varargin)
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%FIND (overloaded)
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%
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% [ind,val] = find(x,k,{'first','last'})
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%
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% Note: If x is zero, the index will be length(x)+1, and the value will be 0
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% Hence, a way to force some element to be non-zero, is to add the
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% constraint ind <= length(x).
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% This also means that you never should use x(ind) if x can be all zeros,
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% but use the second output val instread.
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%
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% FIND is implemented in the nonlinear operator framework using a big-M
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% model.
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switch class(varargin{1})
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case 'double'
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error('Overloaded SDPVAR/FIND 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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x = varargin{1};
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if min(size(x)) > 1
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error('SDPVAR/FIND currenty only support vector arguments');
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end
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x = reshape(x,1,[]);
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if nargin > 1
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if ~(isequal(varargin{2},[]) || isequal(varargin{2},1))
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error('SDPVAR/FIND currenty only support 1 non-zero element (second argument must be 1 or [])');
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end
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end
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k = 1;
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if nargin > 2
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if isequal(varargin{3},'last')
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error('SDPVAR/FIND currenty only supports detecting first non-zero element');
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end
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end
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which = 'first';
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x_extended = [x 1];
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ind = yalmip('define',mfilename,x_extended,k,which);
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varargout{1} = ind;
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if nargout == 2
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x_0 = [x 0];
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varargout{2} = subsref(x_0,struct('type','()','subs',{{ind}}));
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end
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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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X = varargin{3};
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% Call external to allow subsrefs in classs
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F = find_internal(t,X);
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varargout{1} = F;
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varargout{2} = struct('convexity','none','monotonicity','none','definiteness','none','model','integer');
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varargout{3} = X;
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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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