如何根据列中的颜色为条形图着色

Posted 2023-03-11

【中文标题】如何根据列中的颜色为条形图着色

【英文标题】：How to pivot a dataframe to plot bars

【发布时间】：2022-01-10 10:38:32

【问题描述】：

我正在尝试创建一个堆积条形图，并使用我存储在变量 party_color 中的颜色名称为条形着色。

这是我的尝试：

import pandas as pd
import matplotlib.pyplot as plt

marginal_electorates_2016 = 'margin': 0: 'Fairly safe', 1: 'Fairly safe', 2: 'Fairly safe', 3: 'Marginal', 4: 'Marginal', 5: 'Marginal', 6: 'Marginal', 7: 'Safe', 8: 'Safe', 9: 'Safe', 10: 'Safe',
                             'PartyNm': 0: 'Australian Labor Party', 1: "Katter's Australian Party", 2: 'Liberal/National Coalition', 3: 'Australian Labor Party', 4: 'Independent', 5: 'Liberal/National Coalition', 6: 'Nick Xenophon Team', 7: 'Australian Labor Party', 8: 'Independent', 9: 'Liberal/National Coalition', 10: 'The Greens',
                             'count': 0: 32, 1: 1, 2: 29, 3: 24, 4: 1, 5: 28, 6: 1, 7: 13, 8: 1, 9: 19, 10: 1,
                             'party_color': 0: 'red', 1: 'yellow', 2: 'blue', 3: 'red', 4: 'pink', 5: 'blue', 6: 'orange', 7: 'red', 8: 'pink', 9: 'blue', 10: 'green'

marginal_electorates_2016 = pd.DataFrame(marginal_electorates_2016)

         margin                     PartyNm  count party_color
0   Fairly safe      Australian Labor Party     32         red
1   Fairly safe   Katters Australian Party       1      yellow
2   Fairly safe  Liberal/National Coalition     29        blue
3      Marginal      Australian Labor Party     24         red
4      Marginal                 Independent      1        pink
5      Marginal  Liberal/National Coalition     28        blue
6      Marginal          Nick Xenophon Team      1      orange
7          Safe      Australian Labor Party     13         red
8          Safe                 Independent      1        pink
9          Safe  Liberal/National Coalition     19        blue
10         Safe                  The Greens      1       green

plt.figure(figsize=(16, 6))

marginal_electorates_2016.plot(
    kind = 'bar',
    x = ['margin', 'PartyNm'],
    y = 'count',
    stacked = False,
    subplots = True,
    figsize = [10,15],
    sharey = True,
    c = 'party_colour'
    )
plt.tight_layout

【参考方案1】：

绘制条形组的最简单方法是使用pandas.DataFrame.pivot 将数据框从长格式改造成宽格式 创建一个颜色dict，派对为key，颜色为value，绘图时可以传递给color参数。 有多种方法可以将两列转换为dict，其中一列为keys，另一列为values。使用哪种方式并不重要。 How to create a dictionary of two pandas DataFrame columns 直接使用pandas.DataFrame.plot 和kind='bar' 绘制数据框。如果需要，可以将stacked=True 用于堆积条形图，但我不建议这样做，因为它会使数据更难比较。

import pandas as pd
import matplotlib.pyplot as plt

# create the dataframe
df = pd.DataFrame(marginal_electorates_2016)

# transform the shape
dfp = df.pivot(index='margin', columns='PartyNm', values='count')

# display(dfp)
PartyNm      Australian Labor Party  Independent   Katters Australian Party  Liberal/National Coalition  Nick Xenophon Team  The Greens
margin                                                                                                                                 
Fairly safe                    32.0          NaN                        1.0                        29.0                 NaN         NaN
Marginal                       24.0          1.0                        NaN                        28.0                 1.0         NaN
Safe                           13.0          1.0                        NaN                        19.0                 NaN         1.0

# create a colors dict
colors = dict(df[['PartyNm', 'party_color']].drop_duplicates().to_numpy())

# plot
ax = dfp.plot(kind='bar', rot=0, color=colors, figsize=(16, 6))
ax.legend(bbox_to_anchor=(1, 1.02), loc='upper left')

与stacked=True