温室气体排放的饼图

以下程序按“碳当量”的质量描述了温室气体的排放量。数据来自 2007 IPCC 报告。

import numpy as np
import matplotlib.pyplot as plt

# Annual greenhouse gas emissions, billion tons carbon equivalent (GtCe)
gas_emissions = np.array([(r'$\mathrm{CO_2}$-d', 2.2),
                          (r'$\mathrm{CO_2}$-f', 8.0),
                          ('Nitrous\nOxide', 1.0),
                          ('Methane', 2.3),
                          ('Halocarbons', 0.1)],
                         dtype=[('source', 'U17'), ('emission', 'f4')])

# 5 colours beige
colours = ['#C7B299', '#A67C52', '#C69C6E', '#754C24', '#534741']

explode = [0, 0, 0.1, 0, 0]

fig, ax = plt.subplots()
ax.axis('equal')        # So our pie looks round!
ax.pie(gas_emissions['emission'], colors=colours, shadow=True, startangle=90,
       explode=explode, labels=gas_emissions['source'], autopct='%.1f%%',
       pctdistance=1.15, labeldistance=1.3)

plt.show()

百分比值格式化为一位小数 ( autopct='%.1f%%')

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