计算 2D NumPy 数组所有列的和
让我们看看如何计算二维 NumPy 数组所有列的和。
示例:
Input :
[[1, 2, 3, 4, 5],
[5, 6, 7, 8, 9],
[2, 1, 5, 7, 8],
[2, 9, 3, 1, 0]]
Output : [10, 18, 18, 20, 22]
Input :
[[5, 4, 1, 7],
[0, 9, 3, 5],
[3, 2, 8, 6]]
Output : [8, 15, 12, 18]
方法 1 : 我们将使用[sum()](https://www.geeksforgeeks.org/numpy-sum-in-python/)方法。我们将通过参数 axis = 0逐列获取总和。
# importing numpy
import numpy as np
# initialize the 2-d array
arr = np.array([[1, 2, 3, 4, 5],
[5, 6, 7, 8, 9],
[2, 1, 5, 7, 8],
[2, 9, 3, 1, 0]])
# calculating column wise sum
sum_2d = arr.sum(axis = 0)
# displaying the sum
print("Column wise sum is :\n", sum_2d)
输出:
Column wise sum is :
[10 18 18 20 22]
方法二:我们也可以使用**numpy.einsum()**方法，参数'ij->j'。
# importing numpy
import numpy as np
# initialize the 2-d array
arr = np.array([[1, 2, 3, 4, 5],
[5, 6, 7, 8, 9],
[2, 1, 5, 7, 8],
[2, 9, 3, 1, 0]])
# calculating column wise sum
sum_2d = np.einsum('ij->j', arr)
# displaying the sum
print("Column wise sum is :\n", sum_2d)
输出:
Column wise sum is :
[10 18 18 20 22]
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