def linear_func(W,X):
    """
    General form of a 2-d linear function with w0 as intercept
    W = [w0,w1,w2], X = [x1,x2]
    f_x = w0 + w1 * x1 + w2 * x2
    """
    return W[0]+W[1]*X[0]+W[2]*X[1]