anal1.m

这是伯克里wavelet transforms一书中的例子的代码

function an1 =  anal1(x,lo,hi)
%anal1(x,lo,hi) decomposes the input vector, x
% using the analysis filter bank lo,hi. This is 
%a one level decomposition. Orthonormal filter 
%banks used with circular extension.
%
%This routine is used by the routine, anal for 
%orthogonal wavelet decomposition.
% 
%Author: Ajit S. Bopardikar
%Copyright (c) 1998 by Addison Wesley Longman, Inc.
%
 l = length(lo);
 n = length(x);

 ext = [x x(1:l)]; %circular extension

 ll = conv(ext,lo);
 hh = conv(ext,hi);

 ll = ll(l:2:(l+n-1)); %choose the circular convolved part
 hh = hh(l:2:(l+n-1)); %and downsample by two.

 an1 = [ll hh]; %put the low pass and high pass parts together