load cnoislop;
s=cnoislop;
subplot(7,1,1);
plot(s);
Ylabel('s');
title('原始信號和各層近似');
[c,l]=wavedec(s,6,'db3');
for i=1:6
   decom=wrcoef('a',c,l,'db3',7-i);
   subplot(7,1,i+1);
   plot(decom);
   Ylabel(['a',num2str(7-i)]);
end