tools.py 文件源码

def second_order_nic(x):
    """
    transform             
    x1 x2  --->   1 x1 x2 x1x2 x1**2 x2**2

    nic : no initial constant
    """
    ones = np.ones(len(x))
    x1 = x[:, 0]
    x2 = x[:, 1]
    x1_sqr = x1**2
    x2_sqr = x2**2
    x1x2 = x1 * x2
    return np.stack([ones, x1, x2, x1x2, x1_sqr, x2_sqr], axis=1)

# STOCHASTIC GRADIENT DESCENT