%生成含噪斜波信號
N=1000;
t=1:N;
sig(1:500)=3*(1:500)/500;
sig(501:N)=3;
x=sig+randn(1,N);
figure(1);
plot(t,x,'LineWidth',2);xlabel('時間 t/s');ylabel('幅值 A');
%一維小波分解
[c,l] = wavedec(x,6,'db3');
%重構第1～6層逼近系數
a6 = wrcoef('a',c,l,'db5',6);
a5 = wrcoef('a',c,l,'db5',5);
a4 = wrcoef('a',c,l,'db5',4);
a3 = wrcoef('a',c,l,'db5',3);
a2 = wrcoef('a',c,l,'db5',2);
a1 = wrcoef('a',c,l,'db5',1);
%顯示逼近系數
figure(3)
subplot(6,1,1);plot(a6,'LineWidth',2);ylabel('a6');
subplot(6,1,2);plot(a5,'LineWidth',2);ylabel('a5');
subplot(6,1,3);plot(a4,'LineWidth',2);ylabel('a4');
subplot(6,1,4);plot(a3,'LineWidth',2);ylabel('a3');
subplot(6,1,5);plot(a2,'LineWidth',2);ylabel('a2');
subplot(6,1,6);plot(a1,'LineWidth',2);ylabel('a1');
xlabel('時間 t/s');
%重構第1～6層細節系數
d6 = wrcoef('d',c,l,'db5',6);
d5 = wrcoef('d',c,l,'db5',5);
d4 = wrcoef('d',c,l,'db5',4);
d3 = wrcoef('d',c,l,'db5',3);
d2 = wrcoef('d',c,l,'db5',2);
d1 = wrcoef('d',c,l,'db5',1);
%顯示細節系數
figure(4)
subplot(6,1,1);plot(d6,'LineWidth',2);ylabel('d6');
subplot(6,1,2);plot(d5,'LineWidth',2);ylabel('d5');
subplot(6,1,3);plot(d4,'LineWidth',2);ylabel('d4');
subplot(6,1,4);plot(d3,'LineWidth',2);ylabel('d3');
subplot(6,1,5);plot(d2,'LineWidth',2);ylabel('d2');
subplot(6,1,6);plot(d1,'LineWidth',2);ylabel('d1');
xlabel('時間 t/s');