subsref.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 y = subsref(X,Y)
%SUBSREF (overloaded)

% Author Johan L鰂berg 
% $Id: subsref.m,v 1.8 2005/03/02 17:18:38 johanl Exp $   

try
	switch Y.type
	case '()'
		% Check for simple cases to speed things up (yes, ugly but we all want speed don't we!)
		switch size(Y.subs,2)
		case 1
			y = subsref1d(X,Y.subs{1});
		case 2
			y = subsref2d(X,Y.subs{1},Y.subs{2});
		otherwise
			error('Indexation error.');
		end
	otherwise
		error(['Indexation with ''' Y.type ''' not supported']) ;
	end    
catch
	error(lasterr)
end
if isempty(y.lmi_variables)
	y = full(reshape(y.basis(:,1),y.n,y.m));
end

function X = subsref1d(X,ind1)

% Get old and new size
n = X.n;
m = X.m;

% Convert to linear indecicies
if islogical(ind1)
    ind1 = double(find(ind1));
end

% Ugly hack handle detect X(:)
pickall=0;
if ischar(ind1)
	ind1 = (1:n*m);
    pickall=1;
end

% What would the size be for a double
dummy = reshape(X.basis(:,1),n,m);
dummy = dummy(ind1);
nnew = size(dummy,1);
mnew = size(dummy,2);

[nx,mx] = size(X.basis);
% Sparse row-based subsref can be EEEEEEEXTREMELY SLOW IN SOME CASES
% FIX : Smarter approach?
Z = X.basis';
Z = Z(:,ind1);
Z = Z';

% Find non-zero basematrices
nzZ = find(any(Z(:,2:end),1));
if ~isempty(nzZ)
	X.n = nnew;
	X.m = mnew;
	X.lmi_variables =  X.lmi_variables(nzZ);
	X.basis = Z(:,[1 1+nzZ]);
else
	bas = reshape(X.basis(:,1),n,m);
	X.n = nnew;
	X.m = mnew;
	X.lmi_variables = [];
	X.basis = reshape(bas(ind1),nnew*mnew,1);
end

% Fix...
 if pickall   
   X.n = n*m;
   X.m = 1;
end


function X = subsref2d(X,ind1,ind2)

if ischar(ind1)
	ind1 = 1:X.n;
end
if ischar(ind2)
	ind2 = 1:X.m;
end

% Convert to linear indecicies
if islogical(ind1)
    ind1 = double(find(ind1));
end

% Convert to linear indecicies
if islogical(ind2)
    ind2 = double(find(ind2));
end

n = X.n;
m = X.m;
lind2 = length(ind2);
lind1 = length(ind1);
if lind2 == 1
    ind1_ext = ind1(:);
else
    ind1_ext = kron(repmat(1,lind2,1),ind1(:));
end
if lind1 == 1
    ind2_ext = ind2(:);
else
    ind2_ext = kron(ind2(:),repmat(1,lind1,1));
end

if prod(size(ind1_ext))==0 | prod(size(ind2_ext))==0
    linear_index = [];
else
    % Speed-up for some bizarre code with loads of indexing of vector
    if m==1 & ind2_ext==1
        linear_index = ind1_ext;
    else
        linear_index = sub2ind([n m],ind1_ext,ind2_ext);
    end
end
nnew = length(ind1);
mnew = length(ind2);

% Put all matrices in vectors and extract sub matrix
Z = X.basis(linear_index,:);
% Find non-zero basematrices  
nzZ = find(any(Z(:,2:end),1));
if ~isempty(nzZ)
    X.n = nnew;
    X.m = mnew;
    X.lmi_variables =  X.lmi_variables(nzZ);
    X.basis = Z(:,[1 1+nzZ]);
else
    bas = reshape(X.basis(:,1),n,m);
    X.n = nnew;
    X.m = mnew;
    X.lmi_variables = [];
    X.basis = reshape(bas(linear_index),nnew*mnew,1);
end