离散信号或连续信号的小波变换

%例程6－8 方波信号的离散小波变换 % e.g.6-8.m for example6-8; %test the function of dwt clear all; t=0:.01*pi:10*pi; x=square(t,80); X=x+randn(size(x))/10; subplot(311); plot(t,X); xlabel('Time t'); axis([0 11*pi -2 2]); ylabel('Amplitude X'); title('Analyzed signal ') % Perform single-level discrete wavelet transform of X by haar %and the kind of signal extension mode is zero-padding extension. [ca1,cd1] = dwt(X,'haar','mode','zpd'); subplot(323); plot(ca1); title('Approx. coef. for haar'); subplot(324); plot(cd1); title('Detail coef. for haar'); % Perform single-level discrete wavelet transform of X by coif4,use the default mode . % and observe edge effects for last coefficients. [ca2,cd2] = dwt(X,'coif4','mode','sym'); subplot(325); plot(ca2); title('Approx. coef. for coif4'); subplot(326); plot(cd2); title('Detail coef. for coif4');