mmax.m

小波变换极大值推算突变点的奇异度指标

%load freqbrk;
freqbrk=sin(pi*[0:511])+(rand(1,512)-0.5)*2;

%figure(1),plot(freqbrk);title('freqbrk')

figure(2)
wname='db5';
[c,l]=wavedec(freqbrk,5,wname);
A5=wrcoef('a',c,l,wname,5);
D1=wrcoef('d',c,l,wname,1);
D2=wrcoef('d',c,l,wname,2);
D3=wrcoef('d',c,l,wname,3);
D4=wrcoef('d',c,l,wname,4);
D5=wrcoef('d',c,l,wname,5);
subplot(7,1,1);plot(freqbrk);title('u2')
p=localmax(A5,1);
P=p>0;
LMAXA5=P.*A5;
subplot(7,1,2);plot(LMAXA5);title('Approximation A5')
p=localmax(D5,1);
P=p>0;
LMAXD5=P.*D5;
subplot(7,1,3);plot(LMAXD5);title('Detail D5')
p=localmax(D4,1);
P=p>0;
LMAXD4=P.*D4;
subplot(7,1,4);plot(LMAXD4);title('Detail D4')
p=localmax(D3,1);
P=p>0;
LMAXD3=P.*D3;
subplot(7,1,5);plot(LMAXD3);title('Detail D3')
p=localmax(D2,1);
P=p>0;
LMAXD2=P.*D2;
subplot(7,1,6);plot(LMAXD2);title('Detail D2')
p=localmax(D1,1);
P=p>0;
LMAXD1=P.*D1;
subplot(7,1,7);plot(LMAXD1);title('Detail D1')

% 从系数上查看极值：
figure(3);set(3,'Position',[5,40,1010,650]);
subplot(311);plot(s)
wname1='db5';J=5;JJ='5';
[c,l]=wavedec(s,J,wname1);
aJ = appcoef(c,l,wname1,J);
subplot(312);plot(aJ);axis([0 length(aJ) min(aJ) max(aJ)])

subplot(313);
for k=1:J
dk = detcoef(c,l,k);
plot(dk);axis([0 length(dk) min(dk)+0.2*min(dk) max(dk)+0.2*max(dk)])
kk=J-k;
Ylabel(['d' JJ-kk]);
pause
end 

clear