使用np.where pandas 基于多个列的多个条件 [英] pandas multiple conditions based on multiple columns using np.where
问题描述
我试图根据两个条件为熊猫数据框的点着色.示例:
I am trying to color points of an pandas dataframe dependend on TWO conditions. Example:
如果col1的值> a(浮动)AND col2-的值,且col3的值< b(浮点),然后col 4的值=字符串,否则:其他字符串.
If value of col1 > a (float) AND value of col2- value of col3 < b (float), then value of col 4 = string, else: other string.
我现在已经尝试了许多不同的方法,而我在网上找到的所有内容仅取决于一种情况.
I have tried so many different ways now and everything I found online was only depending on one condition.
我的示例代码总是会引发错误: 系列的真值是模棱两可的.使用a.empty,a.bool(),a.item(),a.any()或a.all().
My example code always raises the Error: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().
这是代码.尝试了几种变体而没有成功.
Here's the code. Tried several variations without success.
df = pd.DataFrame()
df['A'] = range(10)
df['B'] = range(11,21,1)
df['C'] = range(20,10,-1)
borderE = 3.
ex = 0.
#print df
df['color'] = np.where(all([df.A < borderE, df.B - df.C < ex]), 'r', 'b')
顺便说一句:我明白,它说了什么,但没有怎么处理... 预先感谢!
Btw: I understand, what it says but not how to handle it... Thanks in advance!
推荐答案
选择条件使用布尔索引:
df['color'] = np.where(((df.A < borderE) & ((df.B - df.C) < ex)), 'r', 'b')
>>> df
A B C color
0 0 11 20 r
1 1 12 19 r
2 2 13 18 r
3 3 14 17 b
4 4 15 16 b
5 5 16 15 b
6 6 17 14 b
7 7 18 13 b
8 8 19 12 b
9 9 20 11 b
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