clc
clear
close all

%IIR
%lowpass
fs=1000;%Sample frequence
fpass=40;
fstop=100;
Wp = fpass/(0.5*fs); Ws = fstop/(0.5*fs);
Rp = 3; Rs = 60;
[n,Wn] = buttord(Wp,Ws,Rp,Rs)
[b,a]= butter(n,Wn);
freqz(b,a,512,fs); title('butter lowpass');