pandas 中的轴是什么意思? [英] What does axis in pandas mean?

问题描述

这是我生成数据帧的代码:

Here is my code to generate a dataframe:

import pandas as pd
import numpy as np

dff = pd.DataFrame(np.random.randn(1,2),columns=list('AB'))

然后我得到了数据框:

+------------+---------+--------+
|            |  A      |  B     |
+------------+---------+---------
|      0     | 0.626386| 1.52325|
+------------+---------+--------+

当我输入命令时:

dff.mean(axis=1)

我得到了:

0    1.074821
dtype: float64

根据pandas的引用，axis=1代表列，我希望命令的结果是

According to the reference of pandas, axis=1 stands for columns and I expect the result of the command to be

A    0.626386
B    1.523255
dtype: float64

所以这是我的问题:pandas 中的轴是什么意思?

So here is my question: what does axis in pandas mean?

推荐答案

它指定了计算均值的轴.默认axis=0.这与 axis 指定显式时的 numpy.mean 用法一致(在 numpy.mean 中，axis==None 默认情况下，它计算扁平数组上的平均值)，其中 axis=0 沿着 rows(即，index inpandas) 和 axis=1 沿 列.为了更加清晰，可以选择指定 axis='index'(而不是 axis=0)或 axis='columns'(而不是axis=1).

It specifies the axis along which the means are computed. By default axis=0. This is consistent with the numpy.mean usage when axis is specified explicitly (in numpy.mean, axis==None by default, which computes the mean value over the flattened array) , in which axis=0 along the rows (namely, index in pandas), and axis=1 along the columns. For added clarity, one may choose to specify axis='index' (instead of axis=0) or axis='columns' (instead of axis=1).

+------------+---------+--------+
|            |  A      |  B     |
+------------+---------+---------
|      0     | 0.626386| 1.52325|----axis=1----->
+------------+---------+--------+
             |         |
             | axis=0  |
             ↓         ↓

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