cont_frac(num,den)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Mario Alberto Coutino Minguez                             %
%                                                          %
%[A_VECTOR B_VECTOR] = CONT_FRACT(NUM,DEN)                 %
%   Computes the continuos fraction expansion of a transfer%
%   function which numerator and denomitador are [num] and %
%   [den] respectively.                                    %
%   The coefficients of the expansion are saved in         %
%   a_vector and b_vector for their further usage.         %
%                                                          %
%                                                          %
%Centro Universitario de Ciencias Exactas e Ingenieras     %
%Universidad de Guadalajara 2013                           %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function [a_vector b_vector]  = cont_frac(num,den)
		
	l_num = length(num);
	l_den = length(den);
	
	coeffs = [];
	
	%Coefficients' Variables	
	a_vector = [];
	b_vector = [];
	aux = [];
	%Flow Variables
	i = 0;
	k = 0;
	j = 1;
	stop = 0;
	
	if (l_num == l_den)
		
		a_vector(1) = num(1) / den(1);
		num = num(2:end) - a_vector(1) *den(2:end);
	else
		if (l_num > l_den)
			disp('error');
		end
	end	
	
	while( stop ~= 1)
	
		aux = num;
		num = den;
		den = aux;	
				
		if (mod(i,2) == 0)
			b_vector(1+k) = num(1)/den(1);
			num = [num(2:end-1) - b_vector(1+k) *den(2:end) num(end)];
			k = k+1;
		else
			a_vector(1+j) = num(1)/den(1);
			num = num(2:end) - a_vector(1+j) *den(2:end);
			j = j+1;
        end		
		 
		if(num == 1)
			stop = 1;
            a_vector(1+j) = den;
        end		
        i = i+1;
    end
end