Code covered by the BSD License

# MIMOtool

### Giampiero Campa (view profile)

12 Nov 2001 (Updated )

Multi Input Multi Output Systems Toolbox

[var,stk]=xtr(stk,pos)
```function [var,stk]=xtr(stk,pos)

% [var,stk]=xtr(stk,pos) extracts from the stack variable
% stk at the position given by pos the variable var.
% The extracted variable var is given as first output argument.
% If a second output argument is required then new value of stk
% (which no more contains var) is returned as the second output.
%
% stk is a stack variable organized as:
%
%       [a1 b1 ... an bn 0            ...                  0 ]
% stk = [n reshape(var1,1,a1*b1)  ...  reshape(varn,1,an*bn) ]
%
% if pos is not specified, then by default the variable extracted
% is the last one (pos=n).
%

% G.C. 13/5/97

if size(stk,1)==2,
% stack not empty

% number of variables in stack
n=stk(2,1);

%  controls on pos
if nargin<2,pos=n;end
if pos>n, pos=n;
elseif pos<1, pos=1;
end

% data from 1 to pos
abv1=stk(1,1:2*(pos-1));
eve1=2:2:2*(pos-1);odd1=eve1-1;
blw1=stk(2,1+[1:sum(abv1(odd1).*abv1(eve1))]);

pnt=abv1(odd1)*abv1(eve1)';
if ~all(size(pnt)), pnt=0; end

% data to be extracted
sz=stk(1,2*pos+[-1:0]);
var=reshape(stk(2,1+pnt+[1:sz(1)*sz(2)]),sz(1),sz(2));

% data from pos+1 to n
abv2=stk(1,2*(pos+1)-1:2*n);
eve2=2:2:2*(n-pos);odd2=eve2-1;
blw2=stk(2,1+pnt+sz(1)*sz(2)+[1:sum(abv2(odd2).*abv2(eve2))]);

else
var=[];n=[];
abv1=[];abv2=[];
blw1=[];blw2=[];
end

if nargout>1,
% gives the new value of the stack

n=n-1;
if n==0, n=[]; end

above=[abv1 abv2];
below=[n blw1 blw2];

% fullfill with zeros the ending unused space
l1=size(above,2);
l2=size(below,2);
if l2>l1,stk=[above zeros(1,l2-l1); below];
else stk=[above; below zeros(1,l1-l2)];
end

end
```