clear
format compact
nntwarn off
P=-1:0.1:-0.5;
T=[-0.9602 -0.5770 -0.0729 0.3771 0.6405 0.6600];
[R,Q]=size(P);
S1=20;
[S2,Q]=size(T);
[W1,B1]=nwtan(S1,R);
[W2,B2]=rands(S2,S1);
disp_freq=100;
max_epoch=10000;
err_goal=0.1;
lr=0.01;
error=[];
A1=tansig(W1*P,B1);
A2=purelin(W2*A1,B2);
E=T-A2;
SSE=sumsqr(E);

for epoch=1:max_epoch
    if SSE < err_goal
        epoch=epoch-1; break
    end

    D2=deltalin(A2,E);
    D1=deltatan(A1,D2,W2);
    [dW1,dB1]=learnbp(P,D1,lr);
    [dW2,dB2]=learnbp(A1,D2,lr);
    W1=W1+dW1;
    B1=B1+dB1;
    W2=W2+dW2;
    B2=B2+dB2;

    A1=tansig(W1*P,B1);
    A2=purelin(W2*A1,B2);
    E=T-A2;
    SSE=sumsqr(E);
    error=[error SSE];

    if(rem(epoch,disp_freq)==0)
        fprintf('\n%d epoch, SSE = %g', epoch, SSE)
        plot(P,T,'r',P,A2,'g')
        pause(1e-10)
    end
end
fprintf('\n\n%d epoch, SSE = %g', epoch, SSE)