% 裝載實際信號
load vonkoch 
vonkoch=vonkoch(1:510); 
lv = length(vonkoch);

subplot(311), plot(vonkoch);title('被分析信號.'); 
set(gca,'Xlim',[0 510])
% 執(zhí)行離散5層sym2小波變換
% 層數(shù)1～5分別對應尺度 2, 4, 8, 16 and 32
[c,l] = wavedec(vonkoch,5,'sym2');

% 擴展離散小波系數(shù)進行畫圖
% 層數(shù)1～5分別對應尺度 2, 4, 8, 16和32
cfd = zeros(5,lv); 
for k = 1:5 
    d = detcoef(c,l,k); 
    d = d(ones(1,2^k),:); 
    cfd(k,:) = wkeep(d(:)',lv); 
end 

cfd = cfd(:); 
I = find(abs(cfd)<sqrt(eps)); 
cfd(I)=zeros(size(I)); 
cfd = reshape(cfd,5,lv);

% 畫出離散系數(shù)
subplot(312), colormap(pink(64)); 
img = image(flipud(wcodemat(cfd,64,'row'))); 
set(get(img,'parent'),'YtickLabel',[]); 
title('離散變換, 系數(shù)絕對值.') 
ylabel('層數(shù)')

% 執(zhí)行連續(xù)小波sym2變換，尺度從1～32
subplot(313)
ccfs = cwt(vonkoch,1:32,'sym2','plot'); 
title('連續(xù)變換, 系數(shù)絕對值.') 
colormap(pink(64)); 
ylabel('尺度')