www.pudn.com > multiwavelet.rar > prep1D_appe.m

function fp=prep1D_appe(f,pflt) 
%fp=prep1D_appe(f,pflt) 
% 
%  This function performs critically sampled preprocessing of given  
%  1-dimensional signal. Boundaries are handled by periodic extension. 
%  For description of the algorithm see [SW] //对于边界是周期扩张 
% 
%  appe: 这是逼近预滤波；这个函数与postp1D_appe.m共同使用； 
% 
%  Input: 
%    pflt       string of characters, name of the prefilter; 
%               for possible names and short descriptions see coef_prep.m 
%    f          1 by n real array, input data; //1-D输入信号 
% 
%    n          n must be of the form r*integer*2^maxlevel, //输入信号的长度 
%    r          r is the number of scaling functions,//尺度函数的个数 
%    maxlevel   maxlevel is the number of levels of multiwavelet transform //多小波分解的层数 
% 
%  Output:   
%    fp         r by n/r real array, preprocessed signal; 
%               each row corresponds to a scaling function  
% 
%  Example of Usage: 
%    fp=prep1D_appe(f,'clap') 
 
% Author: Vasily Strela 
% COPYRIGHT 1997,98 by Vasily Strela 
 
[PR,PO]=coef_prep(pflt); %% 得到预滤波矩阵 
 
n=length(f); 
 
[nf,np]=size(PR); 
np=np/nf; 
 
fs=zeros(nf,round(n/nf)); 
for i=1:round(n/nf) 
  for j=1:nf 
    fs(j,i)=f(nf*(i-1)+j); 
  end 
end 
 
fp=zeros(nf,round(n/nf)); 
for i=1:round(n/nf)-np+1 
  for j=1:np 
    fp(:,i)=fp(:,i)+PR(:,nf*(j-1)+1:nf*j)*fs(:,i+j-1); 
  end 
end 
 
for i=round(n/nf)-np+2:round(n/nf) 
  for j=1:np 
    if i+j-1>round(n/nf) 
      fp(:,i)=fp(:,i)+PR(:,nf*(j-1)+1:nf*j)*fs(:,i+j-1-round(n/nf)); 
    else 
      fp(:,i)=fp(:,i)+PR(:,nf*(j-1)+1:nf*j)*fs(:,i+j-1); 
    end 
  end 
end