doFilter.m

function y = doFilter(x)
%DOFILTER Filters input x and returns output y using a lowpass filter.

% MATLAB Code
% Generated by MATLAB(R) 9.3 and DSP System Toolbox 9.5.
% Generated on: 21-May-2018 11:12:40

persistent Hd;

if isempty(Hd)
    
    Fpass = 0.0104;  %Normalized(0-1) Passband Frequency
    Fstop = 0.0167;  %Noralized(0-1) Stopband Frequency
    Apass = 1;     % Passband Ripple (dB)
    Astop = 60;    % Stopband Attenuation (dB)
    
    h = fdesign.lowpass('fp,fst,ap,ast', Fpass, Fstop, Apass, Astop);
    
    Hd = design(h, 'equiripple', ...
        'MinOrder', 'any', ...
        'StopbandShape', 'flat');
    
    
    
    set(Hd,'PersistentMemory',true);
    
end

y = filter(Hd,x);