clear all;
nntwarn off;
format compact

disp_freq = 100;
max_epoch = 20000;
err_goal = 1e-3;
lr=0.001;
error=[];

X=-1:.1:1;
Y=-1:.1:1;
Z=zeros(length(X), length(Y));

XX = [];
YY = [];
ZZ = [];

for i = 1 : length(X),
    for j = 1 : length(Y),
    XX = [XX X(i)];
    YY = [YY Y(j)];
    Z(i, j) = ((X(i)^2 + Y(j)^2));
    ZZ = [ZZ Z(i, j)];
    end
end;

P = [XX; YY];
[R, Q] = size(P);
S1=10;
[S3,Q]=size(ZZ);
S2=round(sqrt(S1*S3));

[W1, B1] = nwtan (S1, R);
[W2, B2] = nwtan (S2, S1);
[W3, B3] = rands (S3, S2);

A1 = tansig (W1*P, B1);
A2 = tansig (W2*A1, B2);
A3 = purelin (W3*A2, B3);

E = ZZ - 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 = ZZ - A3;
    SSE = sumsqr(E);
    error = [error, SSE];
    if (rem (epoch, disp_freq) == 0),
    epoch
    SSE
% tu można skończyć
    A3_ = zeros (size (Z));
    for i = 1 : length(X),
        for j = 1 : length(Y),
        A1_ = tansig(W1*[X(i); Y(j)], B1);
        A2_ = tansig(W2*A1_, B2);
        A3_(i, j) = purelin(W3*A2_,B3);
        end
    end

    set(gcf,'renderer','painters');
    subplot (1, 2, 1), mesh (X, Y, Z);
    subplot (1, 2, 2), mesh (X, Y, A3_);
    pause (1e-200);
    end
end