Bandpass filter

I want to run a signal through bandpass filter, but the data is sent one by one.

    t=0:0.0000001:1;
    a=sin(2*pi*250*t)+sin(2*pi*500*t);
    wn=[(240*0.00000001/2) (260*0.00000001/2)];
    [B,A]=butter(2,wn,'bandpass');
    for ii=0:length(t)
    z(ii)=filter(B,A,a(ii));
    end

I'm getting wrong data from the filter. What is wrong with the code??

Answer 1

[Jan]

The wn contain very low frequencies. Is this really wanted?

You cannot filter scalars. Try to omit the loop:

z = filter(B,A,a);

If you really have a good reason to filter the data element by element, you have to consider the current status of the filter:

s = [];
z = zeros(1, length(t));  % pre-allocate!
for ii = 1:length(t)      % Not 0:length(t) !
  [z(ii), s] = filter(B, A, a(ii), s);
end