%生成含噪正弦信號
N=1024;
t=1:N;
sig=sin(0.03*t);
figure(1);
plot(t,sig,'LineWidth',2);xlabel('時間 t/s');ylabel('幅值 A');
%疊加信號
x=sig+randn(1,N);
figure(2)
plot(t,x,'LineWidth',2);xlabel('時間 t/s');ylabel('幅值 A');

%一維小波分解
[c,l] = wavedec(x,5,'db3');
%重構第1～5層逼近信號
a5 = wrcoef('a',c,l,'db3',5);
a4 = wrcoef('a',c,l,'db3',4);
a3 = wrcoef('a',c,l,'db3',3);
a2 = wrcoef('a',c,l,'db3',2);
a1 = wrcoef('a',c,l,'db3',1);
%顯示各層逼近信號
figure(3)
subplot(5,1,1);plot(a5,'LineWidth',2);ylabel('a5');
subplot(5,1,2);plot(a4,'LineWidth',2);ylabel('a4');
subplot(5,1,3);plot(a3,'LineWidth',2);ylabel('a3');
subplot(5,1,4);plot(a2,'LineWidth',2);ylabel('a2');
subplot(5,1,5);plot(a1,'LineWidth',2);ylabel('a1');
xlabel('時間 t/s');
%重構第1～4層細節信號
d5 = wrcoef('d',c,l,'db3',5);
d4 = wrcoef('d',c,l,'db3',4);
d3 = wrcoef('d',c,l,'db3',3);
d2 = wrcoef('d',c,l,'db3',2);
d1 = wrcoef('d',c,l,'db3',1);
%顯示各層細節信號
figure(4)
subplot(5,1,1);plot(d5,'LineWidth',2);ylabel('d5');
subplot(5,1,2);plot(d4,'LineWidth',2);ylabel('d4');
subplot(5,1,3);plot(d3,'LineWidth',2);ylabel('d3');
subplot(5,1,4);plot(d2,'LineWidth',2);ylabel('d2');
subplot(5,1,5);plot(d1,'LineWidth',2);ylabel('d1');
xlabel('時間 t/s');