How to design aFIR filter without filter function

please help me implement this as function to take a,b,x and give me y

[farhad vaseghi]

I wanna impeliment this whith a seprate function

and without,without any use of filter() function!!!!!!!!!!!

Answer 1

[Sriram Tadavarty]

Hi Farhad,

This code should do what is asked for. Since, you asked for FIR filter, a will be a scalar with value 1.

function y = filterbax(b,a,x)
% The function expects inputs to be column vectors

    M = length(b);
    N = length(a);
    xbuffer = [];
    ybuffer = [];

    for i = 1:length(x)
        xbuffer = [x(i);xbuffer];
        if length(xbuffer) < M
            index = length(xbuffer);
        else
            index = M;
        end
        if length(ybuffer) < N-1
            yindex = length(ybuffer);
        else
            yindex = N-1;
        end
        y(i) = (1/a(1)).*(sum(b(1:index).*xbuffer(1:index)) - sum(a(2:yindex+1).*ybuffer(1:yindex)));
        ybuffer = [y(i);ybuffer];
    end
    y = y(:); % Return as column vector
end

Note that more optimizations can be done, but this should work.

% In command prompt,
% try the following 
>> b = [2,3];
>> a = [1,0.2];
>> x = randn(10000,1);
>> y = filterbax(b,a,x); % Custom function

% Compare the output from custom written function and MATLAB function
>> y1 = filter(b,a,x); % MATLAB function
>> max(abs(y-y1).^2)

Hope this helps.

Regards,

Sriram

[farhad vaseghi]

hey bro tankes for your try

but as i toled you i wanna impeliment this whith a seprate function

and without any use of filter() function!!!!!!!!!!!

[Sriram Tadavarty]

Hi farhad, This is not the same filter function. The name of the function is placed as filterbax which is independent of filter. The bottom code in the answer is just the test with the inbuilt Matlab function. Hope it clears. Regards, Sriram

[farhad vaseghi]

Tanks Sriram

your a great man

thats the answer

you helped me this day i wish god bless you

tanks bro