iir filter design in matlab

close all; clear all; clc;
 
% Generate input signal
fsamp = 16600; % (Hz)
dt = 1/fsamp; % (secs)
t = 0:dt:0.2;
fsine1 = 100; % (in passband: should remain in filter output)
a=10;
% am=20*log(a);
%fsine2 = 450; % (in stopband: should be removed by filter)
in = a*sin(2*pi*fsine1*t); 
%+ 10*sin(2*pi*fsine2*t);
 
% Plot input signal
figure(1);
plot(t, in);
title('Input');
xlabel('Time (secs)');
ylabel('Amplitude');
grid on;
 
% Design filter
wp = [200 315]; % Passband corner frequency
ws = [180 346.5]; % Stopband corner frequency
rp = 1;   % Passband ripple (dB)
rs = 80;  % Stopband attenuation (dB)
w1 = 2*wp/fsamp;
w2 = 2*ws/fsamp;
[N,wn] = ellipord(w1,w2,rp,rs)
[b,a] = ellip(N,rp,rs,wn);
 
% Plot filter frequency response
[H,W] = freqz(b,a,fsamp);
mag = 20*log(abs(H));
figure(2);
plot(fsamp*W/(2*pi), mag);
title('Frequency Response');
xlabel('Frequency (Hz)');
ylabel('(dB)');
axis tight;
grid on;
 
% Apply filter and plot output
out = filter(b, a,in);
figure(3);
plot(t, out);
xlabel('Time (secs)');
ylabel('Amplitude');
grid on;