Python numpy cumsum() function returns the cumulative sum of the elements along the given axis.

Python numpy cumsum（）函数返回沿给定轴的元素的累积和。

Python numpy cumsum（）语法 (Python numpy cumsum() syntax)

The cumsum() method syntax is:

cumsum（）方法的语法为：

cumsum(array, axis=None, dtype=None, out=None)

• The array can be ndarray or array-like objects such as nested lists.数组可以是ndarray或类似数组的对象，例如嵌套列表。
• The axis parameter defines the axis along which the cumulative sum is calculated. If the axis is not provided then the array is flattened and the cumulative sum is calculated for the result array.axis参数定义沿其计算累计总和的轴。 如果未提供轴，则将数组展平，并为结果数组计算累计和。
• The dtype parameter defines the output data type, such as float and int.dtype参数定义输出数据类型，例如float和int。
• The out optional parameter is used to specify the array for the result.out可选参数用于指定结果数组。

Python numpy cumsum（）示例 (Python numpy cumsum() Examples)

Let’s look at some examples of calculating cumulative sum of numpy array elements.

让我们看一些计算numpy数组元素的累积和的示例。

1.无轴的numpy数组元素的累积和 (1. Cumulative Sum of Numpy Array Elements without axis)

import numpy as nparray1 = np.array([[1, 2],[3, 4],[5, 6]])total = np.cumsum(array1)
print(f'Cumulative Sum of all the elements is {total}')

Output: Cumulative Sum of all the elements is [ 1 3 6 10 15 21]

输出 ： Cumulative Sum of all the elements is [ 1 3 6 10 15 21]

Here, the array is first flattened to [ 1 2 3 4 5 6]. Then the cumulative sum is calculated, resulting in [ 1 3 6 10 15 21].

在此，首先将数组展平为[1 2 3 4 5 6]。 然后，计算累加和，得出[1 3 6 10 15 21]。

2.沿轴的累计总和 (2. Cumulative Sum along the axis)

import numpy as nparray1 = np.array([[1, 2],[3, 4],[5, 6]])total_0_axis = np.cumsum(array1, axis=0)
print(f'Cumulative Sum of elements at 0-axis is:\n{total_0_axis}')total_1_axis = np.cumsum(array1, axis=1)
print(f'Cumulative Sum of elements at 1-axis is:\n{total_1_axis}')

Output:

输出：

Cumulative Sum of elements at 0-axis is:
[[ 1  2][ 4  6][ 9 12]]
Cumulative Sum of elements at 1-axis is:
[[ 1  3][ 3  7][ 5 11]]

3.指定累积和数组的数据类型 (3. Specifying data type for the cumulative sum array)

import numpy as nparray1 = np.array([[1, 2],[3, 4],[5, 6]])total_1_axis = np.cumsum(array1, axis=1, dtype=float)
print(f'Cumulative Sum of elements at 1-axis is:\n{total_1_axis}')

Output:

输出：

Cumulative Sum of elements at 1-axis is:
[[ 1.  3.][ 3.  7.][ 5. 11.]]

Reference: API Doc

参考 ： API文档

翻译自: https://www.journaldev.com/32801/numpy-cumsum-in-python