matplotlib直方圖與圖例

Question

我有這段代碼產生一個直方圖，標識三種類型的字段; 「低」， 「中等」 和 「高」：

import pylab as plt 
import pandas as pd 


df = pd.read_csv('April2017NEW.csv', index_col =1) 
df1 = df.loc['Output Energy, (Wh/h)'] # choose index value and Average 
df1['Average'] = df1.mean(axis=1) 

N, bins, patches = plt.hist(df1['Average'], 30) 

cmap = plt.get_cmap('jet') 
low = cmap(0.5) 
medium =cmap(0.25) 
high = cmap(0.8) 


for i in range(0,4): 
    patches[i].set_facecolor(low) 
for i in range(4,11): 
    patches[i].set_facecolor(medium) 
for i in range(11,30): 
    patches[i].set_facecolor(high) 

plt.xlabel("Watt Hours", fontsize=16) 
plt.ylabel("Households", fontsize=16) 
plt.xticks(fontsize=14) 
plt.yticks(fontsize=14) 
ax = plt.subplot(111) 
ax.spines["top"].set_visible(False) 
ax.spines["right"].set_visible(False) 

plt.show() 

產生這樣的：

如何獲得一個傳說中有三個不同的顏色？

Answer 1

您需要自己創建圖例。爲此，創建一些矩形，圖中未顯示（所謂的代理藝術家）。

#create legend 
handles = [Rectangle((0,0),1,1,color=c,ec="k") for c in [low,medium, high]] 
labels= ["low","medium", "high"] 
plt.legend(handles, labels) 

完整示例：

import matplotlib.pyplot as plt 
import numpy as np 
from matplotlib.patches import Rectangle 

data = np.random.rayleigh(size=1000)*35 

N, bins, patches = plt.hist(data, 30, ec="k") 

cmap = plt.get_cmap('jet') 
low = cmap(0.5) 
medium =cmap(0.25) 
high = cmap(0.8) 


for i in range(0,4): 
    patches[i].set_facecolor(low) 
for i in range(4,11): 
    patches[i].set_facecolor(medium) 
for i in range(11,30): 
    patches[i].set_facecolor(high) 

#create legend 
handles = [Rectangle((0,0),1,1,color=c,ec="k") for c in [low,medium, high]] 
labels= ["low","medium", "high"] 
plt.legend(handles, labels) 

plt.xlabel("Watt Hours", fontsize=16) 
plt.ylabel("Households", fontsize=16) 
plt.xticks(fontsize=14) 
plt.yticks(fontsize=14) 

plt.gca().spines["top"].set_visible(False) 
plt.gca().spines["right"].set_visible(False) 

plt.show()