abs.m

国外专家做的求解LMI鲁棒控制的工具箱,可以相对高效的解决LMI问题

function varargout=abs(varargin)
%ABS (overloaded)
%
% t = abs(x)
%
% The variable t can only be used in convexity preserving
% operations such as t<0, min t etc.

% Author Johan L鰂berg 
% $Id: abs.m,v 1.8 2005/07/20 13:39:00 joloef Exp $



%% ***************************************************
% This file defines a nonlinear operator for YALMIP
%
% It can take three different inputs
% For double inputs, it returns standard double values
% For sdpvar inputs, it genreates a an internal variable
% When first input is 'model' it generates the epigraph

%% ***************************************************
switch class(varargin{1})

    case 'double' % What is the numerical value of this argument (needed for displays etc)
        % SHOULD NEVER HAPPEN, THIS SHOULD BE CAUGHT BY BUILT-IN
        error('Overloaded SDPVAR/ABS CALLED WITH DOUBLE. Report error')

    case 'sdpvar' % Overloaded operator for SDPVAR objects. Pass on args and save them.
        if isreal(varargin{1})
            varargout{1} = yalmip('addextendedvariable',mfilename,varargin{1});
        else
            % For complex args, abs(X) is defined [abs(X(i,j)] in MATLAB
            y = [];
            x = varargin{1};
            for i = 1:size(x,1)
                temp = [];
                for j = 1:size(x,2)
                    temp = [temp norm(ihatethis(x,i,j))];
                end
                y = [y;temp];
            end
            varargout{1} = y;
        end            

    case 'char' % YALMIP send 'graph' when it wants the epigraph or hypograph
        if isequal(varargin{1},'graph')
            t = varargin{2};
            X = varargin{3};            
            varargout{1} = set(-t < X < t);
            varargout{2} = 1; % Convex operator                
        else
            error('SDPVAR/ABS called with CHAR argument?');
        end
    otherwise
        error('Strange type on first argument in SDPVAR/ABS');
end