00 載入擴展庫

import numpy as np
import matplotlib.pyplot as plt

01 默認趨勢線

x=np.linspace(0,10,200)
y=np.sin(x)
plt.plot(x,y)
plt.xlim(0,10)
plt.ylim(-1.5,1.5)
plt.arrow(0,-0.2,np.pi/2,1）

02 給趨勢線增加箭頭

plt.arrow(0,-0.2,np.pi/2,1,
          head_width=0.2,head_length=0.3,width=0.1)

03 設置趨勢線的顏色

plt.arrow(0,-0.2,np.pi/2,1,
          head_width=0.1,head_length=0.3,width=0.05,color='r')

plt.arrow(0,-0.2,np.pi/2,1,
          head_width=0.2,head_length=0.2,width=0.1,
          facecolor='r',edgecolor='g')

04 設置趨勢線的邊界

plt.arrow(0,-0.2,np.pi/2,1,
          head_width=0.2,head_length=0.3,width=0.1,
          facecolor='r',edgecolor='g',
          linewidth=1,linestyle='-.')