tf2sym(G)

function g = tf2sym(G)
%TF2SYM - Numerical Transfer Function to Symbolic Transfer Function
%conversion.
%
% Syntax:  g = tf2sym(G)
%
% Inputs:
%    G - Numerical Transfer Function
%
% Outputs:
%    g - Symbolic Transfer Function
%
% Example: 
%    g11=tf([1 2],[1 2 1]);
%    g12=tf([1 -1],[1 5 6]);
%    g21=tf([1 -1],[1 3 2]);
%    g22=tf([1 2],[1 1]);
%    G=[g11 g12; g21 g22];
%    g=tf2sym(G);
%    pretty(g)
%
% See also: sym2tf, ss2sym
%
% Author: Oskar Vivero Osornio
% email: [e-mail]
% Created: February 2006; 
% Last revision: 25-March-2006;

% May be distributed freely for non-commercial use, 
% but please leave the above info unchanged, for
% credit and feedback purposes

%------------- BEGIN CODE --------------
p=sym('p');
[n,m]=size(G);
g=zeros(n,m);
g=sym(g);
for i=1:n
    for j=1:m
        [num,den]=tfdata(G(i,j),'v');
        l=length(den);
        order=l;
        for k=1:l
            A(order,1)=p^(k-1);
            order=order-1;
        end
        n=num*A;
        d=den*A;
        g(i,j)=n/d;
        clear A;
    end
end

g=simple(g);
%------------- END OF CODE --------------