fid = fopen ( 'C:\MATLAB7\work\30.19.txt','rt');a=fscanf(fid,'%f');s=a(1:12000);ls=length(s);figure(1);subplot(221);plot(s);Ylabel('s');title('原始信号');grid;[c,l]=wavedec(s,3,'db1'); %采用db1小波并对信号进行三层分解\x0bca3=appcoef