pandas 数据框中的随机选择 [英] Random selection in pandas dataframe

问题描述

我正在尝试解决这个更复杂的问题.这是一个较小的问题:

I'm trying to solve this more complicated question. Here's a smaller problem:

给出df

a    b
1    2
5    0
5    9
3    6
1    8

如何创建列C，该列C是同一行df ['a']和df ['b']两个元素之间的随机选择?

How can I create a column C that is a random selection between the two elements of df['a'] and df['b'] of the same row?

因此，给定此伪df，随机运算符将从行#1的(1，2)对中选择行#2的(5，0)对...等等.

So, given this dummy df, the random operator would choose from the pair (1, 2) for row #1, from (5, 0) for row #2...etc.

谢谢

推荐答案

import random

n = 2  # target row number
random.sample(df.iloc[n, :2], 1)  # Pick one number from this row.

对于整个数据框:

>>> df.loc[:, ['a', 'b']].apply(random.sample, args=(1,), axis=1)
0    [1]
1    [5]
2    [9]
3    [3]
4    [8]
dtype: object

清理它以提取单个值:

>>> pd.Series([i[0] for i in df.loc[:, ['a', 'b']].apply(random.sample, args=(1,), axis=1)], index=df.index)
0    1
1    5
2    9
3    3
4    8
dtype: int64

或者利用列'a'的索引为零(False)和列'b'的索引为1(True):

Or taking advantage that column 'a' is indexed at zero (False) and column 'b' is indexed at 1 (True):

>>> [df.iat[i, j] for i, j in enumerate(1 * (np.random.rand(len(df)) < .5))]
[1, 5, 5, 6, 8]

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