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

function transfth=thresh(transf,maxlevel,thresh,threshtype) 
%transfth=thresh(transf,maxlevel,thresh,threshtype) 
% 
%  This function performs soft or hard thresholding of 1 or 2-dimensional  
%  wavelet transform. Scaling coefficients are not thresholded. 
%  For description of soft and hard thresholding methods see [DJ]. 
% 
%  Input: 
%    threshtype  string of characters, either 'hard' or 'soft',  
%                  threshtype='hard' invokes hard thresholding,   
%                  threshtype='soft' invokes soft thresholding,     
%    thresh      real, value of the threshold  
%    maxlevel    integer, number of levels of wavelet decomposition in transf 
%    transf      m by n reall array, wavelet transform of a signal; 
%                m is either the number of scaling functions or m=n, 
%                n must be of the form integer*2^maxlevel; 
%                for structure of transf see [SW] 
% 
%  Output: 
%    transfth    m by n real array, thresholded wavelet coefficients 
% 
% Example od Usage: 
%   transfth=thresh(transf,3,0.75,'hard') 
 
% Author: Vasily Strela 
% COPYRIGHT 1997,98 by Vasily Strela 
 
 
[n01,n02]=size(transf); 
transfth=transf; 
n2=n02/2^maxlevel; 
n1=1; 
if n01==n02, 
  n1=n2; 
end 
 
for i=n1+1:n01, 
  for j=n2+1:n02, 
    if abs(transf(i,j))thresh, 
        transfth(i,j)= transf(i,j)-thresh; 
      end 
    end 
  end 
end 
 
if n01==n02, 
  for i=1:n1, 
    for j=n2+1:n02, 
      if abs(transf(i,j))thresh, 
          transfth(i,j)= transf(i,j)-thresh; 
        end 
      end 
    end 
  end 
  for i=n1+1:n01, 
    for j=1:n2, 
      if abs(transf(i,j))thresh, 
          transfth(i,j)= transf(i,j)-thresh; 
        end 
      end 
    end 
  end 
end