Matplotlib中多列的双y轴

Question

我想在条形图中显示以下数据框，但使用双 y axis，我想在左侧显示 areas 列，在右侧显示 prices 列：

             area1      area2        price1      price2
level               
first       263.16      906.58      10443.32     35101.88
second      6879.83    14343.03      2077.79     4415.53
third      31942.75    60864.24       922.87     1774.47

我尝试了下面的代码，它可以工作但只显示左侧。

import matplotlib.pyplot as plt

df.plot(kind='bar')
plt.xticks(rotation=45, fontproperties="SimHei")
plt.xlabel("")
plt.legend()

谢谢。

Answer 1

如果我理解正确，一种方法可能是这样，但你必须“玩”一下刻度的宽度和位置值：

import pandas as pd
import matplotlib.pyplot as plt

fig = plt.figure(figsize=(12,5)) 
ax = fig.add_subplot(111) 
ax2 = ax.twinx() 

width = 0.1

df.area1.plot(kind='bar', color='red', ax=ax, width=width, position=0 )
df.area2.plot(kind='bar', color='orange', ax=ax, width=width, position=1)
df.price1.plot(kind='bar', color='blue', ax=ax2, width=width, position=2)
df.price2.plot(kind='bar', color='green', ax=ax2, width=width, position=3)

ax.set_ylabel('Area')
ax2.set_ylabel('Price')
ax.legend(["Area1", "Area2"], bbox_to_anchor=(0.8,1.0))
ax2.legend(["Price1", "Price2"], bbox_to_anchor=(0.9,1.0))
plt.show()

另一种方式是这样的：

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure(figsize=(10,5)) 
ax = fig.add_subplot(111) 
ax2 = ax.twinx() 
# ax.set_xticklabels(ax.get_xticklabels(),rotation=45) # Rotation 45 degrees

width = 0.1
ind = np.arange(len(df))

ax.set_ylabel('Area')
ax2.set_ylabel('Price')
ax.set_xlabel('Level')
ax.bar(ind, df.area1, width, color='red', label='area1')
ax.bar(ind + width, df.area2, width, color='orange', label='area2')
ax2.bar(ind + 2*width, df.price1, width, color='blue', label='price1')
ax2.bar(ind + 3*width, df.price2, width, color='green', label='price2')

ax.set(xticks=(ind + 1.5*width), xticklabels=df.index, xlim=[2*width - 1, len(df)])
ax.legend(["Area1", "Area2"], bbox_to_anchor=(1,1))
ax2.legend(["Price1", "Price2"], bbox_to_anchor=(1,0.87))

plt.show()