function W = DeltaSGD(W, X, D)

    alpha = 0.9;
    
    N = 4;
    for k = 1:N
        x = X(k, :)';   %inputs
        d = D(k);       %desired outputs
        
        v = W*x;
        y = Sigmoid(v); %obtained outputs
        
        e = d - y;
        delta = y*(1-y)*e;
        
        dW = alpha*delta*x; %delta rule
        
        W(1) = W(1) + dW(1);
        W(2) = W(2) + dW(2);
        W(3) = W(3) + dW(3);
    end
end