Matplotlib条形图选择颜色，如果值是正值而值是负数 [英] Matplotlib Bar Chart choose color if value is positive vs value is negative

问题描述

我有一个带有正负值的大熊猫DataFrame作为条形图.我想绘制正色绿色"和负值红色"(非常原始...大声笑).如果> 0绿色"，否则我不知道如何通过< 0'红色'?

I have a pandas DataFrame with positive and negative values as a bar chart. I want to plot the positive colors 'green' and the negative values 'red' (very original...lol). I'm not sure how to pass if > 0 'green' else < 0 'red'?

data = pd.DataFrame([[-15], [10], [8], [-4.5]],
                    index=['a', 'b', 'c', 'd'],
                    columns=['values'])
data.plot(kind='barh')

推荐答案

我将为观察值是否大于0创建一个虚拟列.

I would create a dummy column for whether the observation is larger than 0.

In [39]: data['positive'] = data['values'] > 0

In [40]: data
Out[40]: 
   values positive
a   -15.0    False
b    10.0     True
c     8.0     True
d    -4.5    False

[4 rows x 2 columns]

In [41]: data['values'].plot(kind='barh',
                             color=data.positive.map({True: 'g', False: 'r'}))

此外，您可能要注意不要使列名与DataFrame属性重叠. DataFrame.values给出DataFrame的基础numpy数组.名称重叠会阻止您使用df.<column name>语法.

Also, you may want to be careful not to have column names that overlap with DataFrame attributes. DataFrame.values give the underlying numpy array for a DataFrame. Having overlapping names prevents you from using the df.<column name> syntax.

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