% Name:d_zpolse.m
% The function to draw the pole-zero diagram and the impulse response for discrete system
clear;
A=input('Type in the coefficient vector of denominator polynomial:');
B=input('Type in the coefficient vector of numerator polynomial:');
p=roots(A);                                   %求系統(tǒng)極點(diǎn)
q=roots(B);                              	   %求系統(tǒng)零點(diǎn)
p=p';									       %將極點(diǎn)列向量轉(zhuǎn)置為行向量
q=q';								    	   %將零點(diǎn)列向量轉(zhuǎn)置為行向量
x=max(abs([p q 1]));							%確定縱坐標(biāo)范圍
x=x+0.1;
y=x;											%確定橫坐標(biāo)范圍
clf
subplot(2,1,1)
hold on
axis([-x x -y y])								%確定坐標(biāo)軸顯示范圍
w=0:pi/300:2*pi;
t=exp(i*w);
plot(t)											%畫單位園
axis('square')
plot([-x x],[0 0])								%畫橫坐標(biāo)軸
plot([0 0],[-y y])								%畫縱坐標(biāo)軸
text(0.1,x,'jIm[z]')
text(y,1/10,'Re[z]')
plot(real(p),imag(p),'x')						%畫極點(diǎn)
plot(real(q),imag(q),'o')						%畫零點(diǎn)
title('The pole-zero diagram')	                %標(biāo)注標(biāo)題
hold off
subplot(2,1,2)
impz(B,A);
title('The impulse response h(n)')
xlabel('Time index n')