%The Matlab Code for pages 46-48 in our text, for the Associative Memory
%example.

A{1}=[1 1 1 -1
    -1 1 -1 -1
    -1 1 -1 -1
    -1 1 -1 -1];
A{2}=[-1 1 1 1
    -1 -1 1 -1
    -1 -1 1 -1
    -1 -1 1 -1];
A{3}=[1 1 1 -1
    1 -1 -1 -1
    1 1 1 -1
    1 1 1 -1];
A{4}=[-1 1 1 1
    -1 1 -1 -1
    -1 1 1 1
    -1 1 1 1];
A{5}=[1 1 1 -1
    1 1 -1 -1
    1 -1 -1 -1
    1 -1 -1 -1];
A{6}=[-1 1 1 1
    -1 1 1 -1
    -1 1 -1 -1
    -1 1 -1 -1];
T1=A{1}; T2=A{2}; G1=A{3}; G2=A{4}; F1=A{5}; F2=A{6};

gg=colormap(gray);
gg=gg(end:-1:1,:);

subplot(2,3,1)
imagesc(T1)
colormap(gg)
subplot(2,3,2)
imagesc(G1)
subplot(2,3,3)
imagesc(F1)

subplot(2,3,4)
imagesc(T2)
subplot(2,3,5)
imagesc(G2)
subplot(2,3,6)
imagesc(F2)

fprintf('Training patterns are shown.  Press any key to continue...\n');

pause

%**************************************
%The main code starts here!
%**************************************

X=[T1(:) T2(:) G1(:) G2(:) F1(:) F2(:)];
T=[60 60 0 0 -60 -60];
alpha=0.03;
W=randn(1,16);
b=0;
TotalErr=0;
NumPoints=6;

for k=1:60
    idx=randperm(6);

    for j=1:NumPoints
        ThisOut=W*X(:,idx(j))+b;
        ThisErr=T(idx(j))-ThisOut;
    %Update the weights and biases
        W=W+alpha*ThisErr*X(:,idx(j))';
        b=b+alpha*ThisErr;
    end
    EpochErr(k)=norm((W*X+b*ones(1,6))-T);
end

%Run some samples with errors:

close all

for j=1:15
    k=ceil(rand*6);
    TT=A{k}+0.7*randn(size(A{k}));
    h=W*TT(:)+b;
    imagesc(TT); colormap(gg);
    fprintf('Test item is shown.  Your Guess is?\n');
    
    pause
    
    fprintf('The current (rounded) output is: %d\n',round(h));
    if round(h)>30
        fprintf('Matlab Says: T\n');
    elseif round(h)<30 & round(h)>-30
        fprintf('Matlab Says: G\n');
    else
        fprintf('Matlab Says: F\n');
    end
    
    if k==1 | k==2
      fprintf('The selected map was actually T\n\n');
    elseif k==3 | k==4
        fprintf('The selected map was actually G\n\n');
    elseif k==5 | k==6
        fprintf('The selected map was actually F\n\n');
    else
        fprintf('Error\n');
    end
    pause
end