function W = DeltaBatch(W, X, D)

    alpha = 0.9;
    
    dWsum = zeros(3, 1);
    
    N = 4;
    for k = 1:N
        x = X(k, :)';
        d = D(k);
        v = W*x;
        y = Sigmoid(v);
        e = d - y;
        delta = y*(1-y)*e;
        dW = alpha*delta*x;
        dWsum = dWsum + dW;
    end
    dWavg = dWsum/N;
    W(1) = W(1) + dWavg(1);
    W(2) = W(2) + dWavg(2);
    W(3) = W(3) + dWavg(3);
end