clear;
format compact;

P = -1:.1:-.5;
T = [-.9602 -.5770 -.0729 .3771 .6405 .6600 ];
[R,Q] = size(P);
nntwarn off;
S1=13;
S2=7;
[S3,Q] = size(T);
[W1,B1]=nwtan(S1,R);
[W2,B2]=nwtan(S2,S1);
[W3,B3]=rands(S3,S2);
disp_freq=100;
max_epoch= 20000;
err_goal=1e-200;
lr=0.01;
error=[];
A1=tansig(W1*P,B1);
A2=tansig(W2*A1,B2);
A3=purelin(W3*A2,B3);
E=T-A3;
SSE = sumsqr(E);
for epoch=1:max_epoch
    if SSE < err_goal, epoch=epoch-1; break; end;

       D3=deltalin(A3,E);
       D2=deltatan(A2,D3,W3);
       D1=deltatan(A1,D2,W2);

    [dW1, dB1]=learnbp(P, D1, lr);
    [dW2, dB2]=learnbp(A1, D2, lr);
    [dW3, dB3]=learnbp(A2, D3, lr);

W1 = W1 + dW1; B1 = B1 + dB1;
W2 = W2 + dW2; B2 = B2 + dB2;
W3 = W3 + dW3; B3 = B3 + dB3;

A1 = tansig(W1*P,B1);
A2 = tansig(W2*A1,B2);
A3 = purelin(W3*A2,B3);
E = T-A3;
SSE = sumsqr(E);
error = [error SSE];
if (rem(epoch,disp_freq) == 0)
epoch
SSE
plot(P,T,'r',P,A3,'g');
pause(1e-100);
end;

end;
epoch
SSE