www.pudn.com > image_mva_0.rar > invder.m

function data_der=invder(data) 
% data_der=invder(data) 
% inverse 2nd derivative for making data2 matrix for simplisma 
 
% written by K.Artyushkova 
%7/7/1999 
 
[n,m]=size(data); 
for i=1:m 
    Dmf = fourdifft(data(:,i),2); 
    data2=sgolayfilt(Dmf, 3, 15); 
    data_der(:,i)=data2*(-1); 
end 
 
for i=1:n 
   for j=1:m 
        if data_der(i,j)<=0, 
         data_der(i,j)=0; 
      end 
   end 
end