sofm.m

內涵模糊理論與類神經網路的程式碼...提供初學者做研究參考

% ==========================================================
% 
%           Neural Networks A Classroom Approach
%                     Satish Kumar
%             Copyright Tata McGraw Hill, 2004
%
%       MATLAB code that implements the SOFM algorithm
%             Reference: Table 12.8;Page 561
%
% ==========================================================

% MATLAB PROGRAM TI SIMULATE THE SELF ORGANIZING FEATURE MAP
clear all
numpats = 500;
data = 2*[rand(1,numpats);rand(1,numpats)]-1;

figure(1);
plot(data(1,:),data(2,:),'b.');
drawnow

maxneuron=8;	% max number of neurons on an axis
instarx=2*rand(maxneuron)-1;	% initialise wts
instary=2*rand(maxneuron)-1;

nbd = 6;					% define the max nbd size
contractnbd = 1;		% define contraction rates 
count = 0;				% count to contract every 200 epochs
figure(2);
axis([-1 1 -1 1]);

for epoch = 1:numpats*maxneuron
   count = count + 1;
      
   eta=0.9*(1 - epoch/1000);
    
   if (epoch > 999) eta = 0.005;
   end
    
   for p = 1:numpats		
      for indx = 1:maxneuron
         for indy = 1:maxneuron
            dist(indx,indy)=sqrt((instarx(indx,indy)-data(1,p))^2 ...
               + (instary(indx,indy)-data(2,p))^2);
         end
      end
      
      [val1,rows]=min(dist);	      
      [val2,cols]=min(val1);
      indxmin=rows(cols);
      indymin=cols;
              
      for i=indxmin-nbd:indxmin+nbd
         for j=indymin-nbd:indymin+nbd
            if((i >= 1)&(i<=maxneuron)&(j>=1)&(j<=maxneuron))
               instarx(i,j)=instarx(i,j)+eta*(data(1,p)-instarx(i,j));
               instary(i,j)=instary(i,j)+eta*(data(2,p)-instary(i,j));
            end
         end
      end
   end
   
   for i=1:maxneuron
      plot(instarx(i,:),instary(i,:),'b.');
   end
       
   for i=1:maxneuron
      for j=1:maxneuron
         nb=[1 i-1 j
             2 i+1 j
             3 i   j-1
             4 i   j+1];
          for k=1:4
             if((nb(k,2)>=1)&(nb(k,2)<=maxneuron)&(nb(k,3)>=1)&(nb(k,3)<=maxneuron))
                line([instarx(i,j),instarx(nb(k,2),nb(k,3))],...
                     [instary(i,j),instary(nb(k,2),nb(k,3))]);
               end
            end
         end
      end
      
      drawnow
        
      if count == 200
         nbd = nbd - contractnbd;
         if (nbd < 1) nbd = 1;
         end
         count = 0;
      end
      epoch
   end