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# Zero phase filtering of FIR from filter and Analysis Toolbox

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joms on 19 Mar 2019
How can i use filtfilt function in this filter
% MATLAB Code
% Generated by MATLAB(R) 8.2 and the Signal Processing Toolbox 6.20.
% Generated on: 18-Mar-2019 12:11:31
% Equiripple Lowpass filter designed using the FIRPM function.
% All frequency values are in Hz.
data = xlsread('Smoothendata2.xlsx',1);% read csv content
d1 = data(:,1); % Original Time Vector
d2 = data(:,2); % Original Data Vector
L = length(d1);
tv = linspace(min(d1), max(d1), L); % Time Vector For Interpolation
dv = interp1(d1, d2, tv, 'linear'); % Interpolated Data Vector
Ts = mean(diff(tv)); % Sampling Time Interval
t_stats = [Ts std(tv)];
Fs = 1/Ts; % Sampling Frequency
Fn = Fs/2; % Nyquist Frequency
FTD = fft(dv)/L; % Fourier Transform
Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector
Iv = 1:length(Fv); % Index Vector
figure(1)
semilogy(Fv, abs(FTD(Iv))*2) % Plot Fourier Transform
grid
xlabel('Frequency (Hz)')
ylabel('Amplitude')
%
Fpass = 50; % Passband Frequency
Fstop = 60; % Stopband Frequency
Dpass = 0.17099735734; % Passband Ripple
Dstop = 1; % Stopband Attenuation
dens = 20; % Density Factor
% Calculate the order from the parameters using FIRPMORD.
[N, Fo, Ao, W] = firpmord([Fpass, Fstop]/(Fs/2), [1 0], [Dpass, Dstop]);
% Calculate the coefficients using the FIRPM function.
b = firpm(N, Fo, Ao, W, {dens});
Hd = dfilt.dffir(b);
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