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Book4_Ch03_Python_Codes/Bk4_Ch3_02.py

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+
+###############
+# Authored by Weisheng Jiang
+# Book 4  |  From Basic Arithmetic to Machine Learning
+# Published and copyrighted by Tsinghua University Press
+# Beijing, China, 2022
+###############
+
+# Bk4_Ch3_02.py
+
+import numpy as np
+from matplotlib import pyplot as plt
+import seaborn as sns
+
+u = [0,0,4, 3]
+v = [0,0,-2,4]
+u_bis = [4,3,v[2],v[3]]
+w = [0,0,2,7]
+
+fig, ax = plt.subplots()
+
+plt.quiver([u[0], u_bis[0], w[0]],
+           [u[1], u_bis[1], w[1]],
+           [u[2], u_bis[2], w[2]],
+           [u[3], u_bis[3], w[3]],
+           angles='xy', scale_units='xy', 
+           scale=1, color=sns.color_palette())
+
+plt.axvline(x=0, color='grey')
+plt.axhline(y=0, color='grey')
+
+plt.text(3, 1, r'$||\vec{u}||_2$', 
+         color=sns.color_palette()[0], size=12,
+         ha='center',va='center')
+
+plt.text(3, 6, r'$||\vec{v}||_2$', 
+         color=sns.color_palette()[1], size=12,
+         ha='center',va='center')
+
+plt.text(0, 4, r'$||\vec{u}+\vec{v}||_2$', 
+         color=sns.color_palette()[2], size=12,
+         ha='center',va='center')
+
+plt.ylabel('$x_2$')
+plt.xlabel('$x_1$')
+plt.axis('scaled')
+ax.set_xticks(np.arange(-2,8 + 1))
+ax.set_yticks(np.arange(-2,8 + 1))
+ax.set_xlim(-2, 8)
+ax.set_ylim(-2, 8)
+ax.grid(linestyle='--', linewidth=0.25, color=[0.5,0.5,0.5])
+
+# reference: Essential Math for Data Science