MATLAB: How to implement a generic ‘filter’ function using direct form I

filterMATLAB

I need a code for the filter function in direct form I, like as I implemented a filter function in direct form II transposed below:
function[y] = filtro(a,b,x)
% Generic filter function in direct form II transposed
    N = size(b,2) - 1;% filter order 
    y = zeros(size(x)); % Initializes y with zeros
    %% FOR THE CASE FIR
    if not(size(a,2) == size(b,2))
        a(1) = 1;
        a = zeros(size(b));
    end
    %% Recursive implementation of equations to differences
    aux = zeros(1,N); 
    for r = 1 :size(x,2)      
        y(r) = b(1)*x(r) + aux(1);
        for n = 2 : N   
            aux(n-1) = b(n)*x(r) + aux(n);
            aux(n-1) = aux(n-1)- a(n)*y(r);
        end
        aux(N) = b(N+1)*x(r) - a(N+1)*y(r);
    end
end % END OF FUNCTION
Thanks!

Best Answer

filterdf1 = @(a,b,x) filter( dfilt.df1(a,b), x);
This is a three-argument filter function that uses direct type 1 form.
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