opDiag.m

classdef opDiag < opSpot
    %OPDIAG   Diagonal operator.
    %
    %   opDiag(D) creates an operator for multiplication by the
    %   diagonal matrix that has a vector D on its diagonal.
    %
    %   See also diag.
    
    %   Copyright 2009, Ewout van den Berg and Michael P. Friedlander
    %   See the file COPYING.txt for full copyright information.
    %   Use the command 'spot.gpl' to locate this file.
    
    %   http://www.cs.ubc.ca/labs/scl/spot
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Properties
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    properties( SetAccess = private )
        diag     % Diagonal entries
    end
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Methods - Public
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    methods
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % opDiag. Constructor
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function op = opDiag(d)
            if nargin ~= 1
                error('Invalid number of arguments.');
            end
            
            % Vectorize d and get size
            d = d(:);
            n = length(d);
            
            % Construct operator
            op = op@opSpot('Diag',n,n);
            op.cflag      = ~isreal(d);
            op.diag       = d(:);
            op.sweepflag  = true;
        end % function opDiag
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % double
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function A = double(op)
            A = diag(op.diag);
        end
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % transpose
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function opOut = transpose(op)
            opOut = op;
        end
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % conj
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function opOut = conj(op)
            opOut = opDiag(conj(op.diag));
        end
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % ctranpose
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function opOut = ctranspose(op)
            opOut = opDiag(conj(op.diag));
        end
        
    end % methods - public
    
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % Methods - protected
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    methods( Access = protected )
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % multiply
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function y = multiply(op,x,mode)
            if mode == 1
                y = bsxfun(@times,op.diag,x);
            else
                y = bsxfun(@times,conj(op.diag),x);
            end
        end % function multiply
        
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        % divide
        %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        function x = divide(op,b,mode)
            if mode == 1
                x = bsxfun(@ldivide,op.diag,b);
            else
                x = bsxfun(@ldivide,conj(op.diag),b);
            end
        end % function divide
        
    end % methods - protected
    
end % classdef