function [Y,X] = dm2sr(A,B,C,D,E,T,u0,x0);
% [Y,X] = dm2sr(A,B,C,D,E,T,u0,x0);
% Descriptor matrix to impulse response.
% NB At the moment - this assumes that E is unity .....
% A,B,C,D,E - descriptor matrices
% T vector of time points
% u0 input gain vector: u = u0*unit step.
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% Version control history
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% %% $Id$
% %% $Log$
% %% Revision 1.4 1996/08/15 08:34:08 peter
% %% Added step gain (u0) and initial condition (x0)
% %%
% %% Revision 1.3 1996/08/11 19:33:24 peter
% %% Replaced exp by expm - whoops!
% %%
% %% Revision 1.2 1996/08/11 10:37:40 peter
% %% Corrected mistake in step-response calculation.
% %%
% %% Revision 1.1 1996/08/11 09:42:40 peter
% %% Initial revision
% %%
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
[Ny,Nu] = size(D);
[Ny,Nx] = size(C);
if nargin<7
u0 = zeros(Nu,1);
u0(1) = 1;
end;
if nargin<8
x0 = zeros(Nx,1);
end;
[N,M] = size(T);
if M>N
T = T';
N = M;
end;
one = eye(Nx);
Y = zeros(N,Ny);
X = zeros(N,Nx);
i = 0;
for t = T'
i=i+1;
if Nx>0
expAt = expm(A*t);
x = ( A\(expAt-one) )*B*u0 + expAt*x0;
X(i,:) = x';
if Ny>0
y = C*x + D*u0;
Y(i,:) = y';
end;
elseif Ny>0
y = D*u0;
Y(i,:) = y';
end;
end;