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

function transfcomp=keepnlarge(transf,nbigc) 
%transfcomp=keepnlarge(transf,nbigc) 
% 
%  This function keeps given number of largest elements in an input array and 
%  sets the rest of the array to zero. It can be used as the simplest 
%  compression tool and for comparison of performance of different transforms.  
%  For comparison of several scalar and multiwavelet transforms using this  
%  function see [SW1].  
% 
%  Input:                                                  
%    nbigc       integer, number of largest coefficients to keep 
%    transf      m by n real array, transform of a signal  
% 
%  Output:    
%    transfcomp  m by n real array, nbigc largest coefficients are the same 
%                as in transf and the rest is zero 
% 
%  Example of Usage: 
%   transfcomp=keepnlarge(transf,1024)  
 
% Author: Vasily Strela 
% COPYRIGHT 1997,98 by Vasily Strela 
 
 
[n1,n2]=size(transf); 
N=n1*n2; 
transfcomp=zeros(n1,n2); 
lon=zeros(1,N); 
 
if n1>n2 
  for i=1:n2 
    lon((i-1)*n1+1:i*n1)=abs(transf(:,i)); 
  end 
  [slon,ind]=sort(lon); 
  for i=1:nbigc 
    a=rem(ind(N-i+1)-1,n1); 
    b=ceil(ind(N-i+1)/n1); 
    transfcomp(a+1,b)=transf(a+1,b); 
  end 
else 
  for i=1:n1 
    lon((i-1)*n2+1:i*n2)=abs(transf(i,:)); 
  end 
  [slon,ind]=sort(lon); 
  for i=1:nbigc 
    a=rem(ind(N-i+1)-1,n2); 
    b=ceil(ind(N-i+1)/n2); 
    transfcomp(b,a+1)=transf(b,a+1); 
  end   
end