test_polynomial.py 文件源码

def test_polyfit(self):
        c = np.array([3., 2., 1.])
        x = np.linspace(0, 2, 7)
        y = np.polyval(c, x)
        err = [1, -1, 1, -1, 1, -1, 1]
        weights = np.arange(8, 1, -1)**2/7.0

        # check 1D case
        m, cov = np.polyfit(x, y+err, 2, cov=True)
        est = [3.8571, 0.2857, 1.619]
        assert_almost_equal(est, m, decimal=4)
        val0 = [[2.9388, -5.8776, 1.6327],
                [-5.8776, 12.7347, -4.2449],
                [1.6327, -4.2449, 2.3220]]
        assert_almost_equal(val0, cov, decimal=4)

        m2, cov2 = np.polyfit(x, y+err, 2, w=weights, cov=True)
        assert_almost_equal([4.8927, -1.0177, 1.7768], m2, decimal=4)
        val = [[8.7929, -10.0103, 0.9756],
               [-10.0103, 13.6134, -1.8178],
               [0.9756, -1.8178, 0.6674]]
        assert_almost_equal(val, cov2, decimal=4)

        # check 2D (n,1) case
        y = y[:, np.newaxis]
        c = c[:, np.newaxis]
        assert_almost_equal(c, np.polyfit(x, y, 2))
        # check 2D (n,2) case
        yy = np.concatenate((y, y), axis=1)
        cc = np.concatenate((c, c), axis=1)
        assert_almost_equal(cc, np.polyfit(x, yy, 2))

        m, cov = np.polyfit(x, yy + np.array(err)[:, np.newaxis], 2, cov=True)
        assert_almost_equal(est, m[:, 0], decimal=4)
        assert_almost_equal(est, m[:, 1], decimal=4)
        assert_almost_equal(val0, cov[:, :, 0], decimal=4)
        assert_almost_equal(val0, cov[:, :, 1], decimal=4)