filtfilt for filter.m ?

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Abdul Rauf Anwar
Abdul Rauf Anwar on 6 Mar 2012
Hi I am trying to implement a bandpass filter for EEG data like given below
H = fdesign.bandpass ('Fst1,Fp1,Fp2,Fst2,Ast1,Ap,Ast2',0.05,0.1,200,220,50,0.5,50,1000);
D = design(H,'kaiserwin'); % filter
fvtool(D) % filter's magnitude response
x=randn(1,100000);
y = filter(D,x);
xdft = fft(x);
ydft = fft(y);
subplot(221);semilogy(abs(xdft(1:length(x)/2+1)));
subplot(222);semilogy(abs(ydft(1:length(x)/2+1)));
subplot(223);plot(x);
subplot(224);plot(y);
It seems to work fine as i can see only my desired band of frequences in power spectrum but filtered time domain signal (y) seems to be overdamped for some startup time. I have looked for this problem and it looks like i should use filtfilt instead of filter, can someone guide me how to use filtfilt in above code. Thanks in Anticipation Regards

Answers (1)

Malcolm Lidierth
Malcolm Lidierth on 30 Mar 2012
If you have R2011b+ (or a+?), using the standard filtfilt. If not, see http://www.mathworks.com/matlabcentral/fileexchange/17061-filtfilthd

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