zero phase spectrum and filtfilt function

    Fs = 1;  % Sampling Frequency
    N    = 50;      % Order
    Fc1  = 1/f1;%7s   % First Cutoff Frequency
    Fc2  = 1/f2;     % Second Cutoff Frequency
    flag = 'scale';  % Sampling Flag
% Create the window vector for the design algorithm.
   win = hamming(N+1);
% Calculate the coefficients using the FIR1 function.
    [b,a] = fir1(N, [Fc1 Fc2]/(Fs/2), 'bandpass', win, flag);
% Hd = dfilt.dffir(b);
    out=filtfilt(b,a,data);

if using filter function ,we can get spectrum and phase using fvtool , while using filtfilt , how can i get the two lines?

Answer 1

[Star Strider]

With your [b,a] vectors, use the freqz function to get the Bode plot.

[Roger]

freqz(b,a) is just the fir filter spectrum, i mean the zero phase spectrum.

[Star Strider]

What do you mean ‘zero phase spectrum’?

The Bode plot gives you the magnitude and phase. That’s all you need.