h=[-4 1 -1 -2 5 6 5 -2 -1 1 -4];
n=0:length(h)-1;
k=0:1:500;
w=pi*k/500;
hr=h*exp(-j*n'*w);
realh=real(hr);
imagh=imag(hr);
magh=abs(hr);
angh=angle(hr);
subplot(2,2,1),stem(n,h),title('impulse response');grid on;
subplot(2,2,2),stem(0:L,a),title('a(n) coefficients');grid on;
subplot(2,2,3),plot(w/pi,hr),title('frequncy in pi units');grid on;
subplot(2,2,4),zplane(h,1),title('Type 1 amplitude response');grid on;