如何在Python中垂直连接两个数组? [英] How to vertically concatenate two arrays in Python?

问题描述

我想使用NumPy包在Python中垂直连接两个数组:

a = array([1,2,3,4])
b = array([5,6,7,8])

我想要这样的东西:

c = array([[1,2,3,4],[5,6,7,8]])

如何使用concatenate函数做到这一点?我检查了这两个函数，但结果是相同的:

c = concatenate((a,b),axis=0)
# or
c = concatenate((a,b),axis=1)

我们在以下两个功能中都有此功能:

c = array([1,2,3,4,5,6,7,8])

解决方案

问题是a和b都是一维数组，因此只有一个轴可以将它们连接在一起.

相反，您可以使用 vstack (对于垂直为 v ):

>>> np.vstack((a,b))
array([[1, 2, 3, 4],
       [5, 6, 7, 8]])

此外，row_stack是vstack函数的别名:

>>> np.row_stack((a,b))
array([[1, 2, 3, 4],
       [5, 6, 7, 8]])

还值得注意的是，可以一次堆叠相同长度的多个数组.例如，np.vstack((a,b,x,y))将有四行.

在内部，vstack的工作方式是确保每个数组至少具有二维(使用atleast_2D)，然后调用concatenate在第一轴(axis=0)上联接这些数组. >

I want to concatenate two arrays vertically in Python using the NumPy package:

a = array([1,2,3,4])
b = array([5,6,7,8])

I want something like this:

c = array([[1,2,3,4],[5,6,7,8]])

How we can do that using the concatenate function? I checked these two functions but the results are the same:

c = concatenate((a,b),axis=0)
# or
c = concatenate((a,b),axis=1)

We have this in both of these functions:

c = array([1,2,3,4,5,6,7,8])

解决方案

The problem is that both a and b are 1D arrays and so there's only one axis to join them on.

Instead, you can use vstack (v for vertical):

>>> np.vstack((a,b))
array([[1, 2, 3, 4],
       [5, 6, 7, 8]])

Also, row_stack is an alias of the vstack function:

>>> np.row_stack((a,b))
array([[1, 2, 3, 4],
       [5, 6, 7, 8]])

It's also worth noting that multiple arrays of the same length can be stacked at once. For instance, np.vstack((a,b,x,y)) would have four rows.

Under the hood, vstack works by making sure that each array has at least two dimensions (using atleast_2D) and then calling concatenate to join these arrays on the first axis (axis=0).

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