clear all
nntwarn off
format compact

P = [-1:.1:-.5];
T = [-.9602, -.5770, -.0729, .3771, .6405, .6600];

[R, Q] = size(P);
S1 = 1;
[S2, Q] = size(T);
[W1, B1] = nwtan(S1, R);
[W2, B2] = rands(S2, S1);
disp_freq = 100;
max_epoch = 20000;
err_goal = 1e-20;
lr = 0.1;
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)
        epoch
        SSE
        plot(P, T, 'r', P, A2, 'g')
        pause(1e-10)
    end;
end;