Matlab FIR滤波器最大绝对误差

Question

如何确定滤波器的最大绝对误差（阻带和通带最大纹波）？

% frequencies and amplitudes
f = [0.0 0.45 0.55 1.0];
a = [1.0 1.0 0.0 0.0];
% Parks-McCellan optimal FIR filter with N+1 (11) coefficients
[b, err, res] = firpm(10,f,a);
% impulse response
subplot(2,3,1);
stem(b);
title('Impulse response');

% frequency response of filter
[h,w] = freqz(b,256);
% magnitude of frequency response
subplot(2,3,2);
plot(abs(h));
title('Magnitude response')
% phase of frequency response
subplot(2,3,3);
plot(angle(h));
title('Phase response')