英文:
Does specifying brackets for 1D arrays like [[ ]] make any change in the structure?
问题
以下是要翻译的内容：
这个p = np.array([[mu, sig]])与仅指定np.array([mu, sig])有何不同？
英文:
Does this p = np.array([[mu, sig]]) make any change than just specifying np.array([mu, sig])?
答案1
得分: 2
是的，这两个表达式有区别。
[mu, sig] 是一个包含两个元素（mu 和 sig）的数组。
[[mu, sig]] 是一个包含一个数组的数组。那个数组就是 [mu, sig]，它也是一个包含两个元素（mu 和 sig）的数组。所以 [[mu, sig]] 是一个二维数组（即数组的数组）。
编辑： 我最初说[[mu, sig]]是一个包含一个元素的数组。虽然这是我对多维数组的理解方式，但由于这并不完全正确，这在评论中引发了讨论。[[mu, sig]]仍然有两个元素，只是它们以二维的方式组织起来。
说[[mu, sig]]只有一个元素就像说以下矩阵只有两个元素一样：
[ [1, 2, 3],
[4, 5, 6] ]
鉴于此，为了不让任何人感到困惑，我编辑了我的答案以澄清：[[mu, sig]]是一个包含一个数组的数组。不能完全正确地说它只有一个元素。
英文:
Yes, there is a difference between the two expressions.
[mu, sig] is an array with two elements (mu and sig).
[[mu, sig]] is an array with one array inside it. That one array is [mu, sig], an array with two elements (mu and sig). So [[mu, sig]] is a two dimensional array (i.e. an array of arrays).
Edit: I originally said that [[mu, sig]] is an array with one element inside it. While that is the way I think about multi-dimensional arrays, it sparked a discussion in the comments because that is not 100% correct. [[mu, sig]] still has two elements, only that they are organized in a two dimensional fashion.
Saying that [[mu, sig]] has one element would be like saying that the following matrix has only two elements:
[ [1, 2, 3],
[4, 5, 6] ]
In light of this, and in order not to confuse anyone, I've edited my answer to clarify: [[mu, sig]] is an array with one array inside it. It is not fully correct to say that it has only one element inside it.
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