from mxnet import nd
n_train, n_test, true_w, true_b = 100, 100, [1.2, -3.4, 5.6], 5
features = nd.random.normal(shape=(n_train + n_test, 1))
poly_features = nd.concat(features, nd.power(features, 2),
nd.power(features, 3))
labels = (true_w[0] * poly_features[:, 0] + true_w[1] * poly_features[:, 1] + true_w[2] * poly_features[:, 2] + true_b)
labels += nd.random.normal(scale=0.01, shape=labels.shape)
print(labels[:2])
因为features
和poly_features
的形状都是2D NDARRAY,所以我认为该代码的输出是以下形式:
NDArray 2x1 @cpu(0)
,
,但实际输出形式为
NDArray 2 @cpu(0)
。
为什么输出不是2D ndarray?
,而 features
和 poly_features
是2D ndarray,当您计算labels
时,您仅使用poly_features
的切片,即1d Ndarrays。这是无线电代码分布:
labels = true_w[0] * poly_features[:, 0] # true_w[0] is scalar, poly_features[:, 0] is 1D NDAarray
+ true_w[1] * poly_features[:, 1] # true_w[1] is scalar, poly_features[:, 1] is 1D NDAarray
+ true_w[2] * poly_features[:, 2] # true_w[2] is scalar, poly_features[:, 2] is 1D NDAarray
+ true_b # true_b is scalar
所以,您得到1D数组作为答案。