在圖表外創建一個圖例

Question

在我的一張圖中，我使用了一個輔助軸。我的代碼創建了兩個不同的圖例，並在我的圖中顯示了圖例。這是我的代碼：

fig3 = plt.figure() 
ax3 = fig3.add_subplot(111) 
ax4 = fig3.add_subplot(111) 

ax4 = ax3.twinx() 
line6 = ax3.plot(threshold, different_costs, '-r', label = 'Costs differences', linewidth = 2.0) 
line7 = ax4.plot(threshold, costs1, '-b', label = 'Costs of Model 1 (OFF)', linewidth = 2.0) 
line9 = ax4.plot(threshold, costs2, '-y', label = 'Costs of Model 2 (STANDBY)', linewidth = 2.0) 

ax3.set_xlabel("Threshold") 
ax3.set_ylabel("Costs savings") 
ax4.set_ylabel("Total costs") 

plt.suptitle("Costs savings of using MODEL 1") 
plt.legend() 

plt.show() 

如何用三個標籤創建一個圖例？我如何在圖表外顯示這個圖例？

Answer 1

在您的這部分代碼：

line6 = ax3.plot(threshold, different_costs, '-r', label = 'Costs differences', linewidth = 2.0) 
line7 = ax4.plot(threshold, costs1, '-b', label = 'Costs of Model 1 (OFF)', linewidth = 2.0) 
line9 = ax4.plot(threshold, costs2, '-y', label = 'Costs of Model 2 (STANDBY)', linewidth = 2.0) 

讓所有的線到同一傳說，寫：

lns = line6 + line7 + line9 
labels = [l.get_label() for l in lns] 
plt.legend(lns, labels) 

爲了讓劇情之外你的傳奇，是指這個答案How to put the legend out of the plot，你可以寫：

plt.legend(lns, labels, loc='upper right', bbox_to_anchor=(0.5, -0.05)) 

對於一些樣本數據：

fig3 = plt.figure() 
ax3 = fig3.add_subplot(111) 
ax4 = fig3.add_subplot(111) 

ax4 = ax3.twinx() 
line6 = ax3.plot(range(0,10), range(0,10), '-r', label = 'Costs differences', linewidth = 2.0) 
line7 = ax4.plot(range(10,15), range(10,15), '-b', label = 'Costs of Model 1 (OFF)', linewidth = 2.0) 
line9 = ax4.plot(range(0,5), range(0,5), '-y', label = 'Costs of Model 2 (STANDBY)', linewidth = 2.0) 

ax3.set_xlabel("Threshold") 
ax3.set_ylabel("Costs savings") 
ax4.set_ylabel("Total costs") 

plt.suptitle("Costs savings of using MODEL 1") 

lns = line6 + line7 + line9 
labels = [l.get_label() for l in lns] 
plt.legend(lns, labels, loc='upper right', bbox_to_anchor=(0.5, -0.05)) 

plt.show()