子图的操作

1. 读数据绘图：

   import pandas as pd
   from pandas.plotting import register_matplotlib_converters
   
   unrate = pd.read_csv('unrate.csv')
   unrate['DATE'] = pd.to_datetime(unrate['DATE'])
   first_twelve = unrate[0:12]
   plt.plot(first_twelve['DATE'], first_twelve['VALUE'])
   plt.xticks(rotation=90)
   plt.xlabel('Month')
   plt.ylabel('Unemployment Rate')
   plt.title('Monthly Unemployment Trends, 1948')
   plt.show()
   

   运行结果：
   

2. 绘图

   import numpy as np
   fig = plt.figure()
   #fig = plt.figure(figsize=(3, 3))
   ax1 = fig.add_subplot(2,1,1)
   ax2 = fig.add_subplot(2,1,2)
   
   ax1.plot(np.random.randint(1,5,5), np.arange(5))
   ax2.plot(np.arange(10)*3, np.arange(10))
   plt.show()
   

   运行结果：
   

3. 一图画两条线

   unrate['MONTH'] = unrate['DATE'].dt.month
   unrate['MONTH'] = unrate['DATE'].dt.month
   fig = plt.figure(figsize=(6,3))
   
   plt.plot(unrate[0:12]['MONTH'], unrate[0:12]['VALUE'], c='red')
   plt.plot(unrate[12:24]['MONTH'], unrate[12:24]['VALUE'], c='blue')
   plt.show()
   

   运行结果：
   

4. 循环绘图

   fig = plt.figure(figsize=(10,6))
   colors = ['red', 'blue', 'green', 'orange', 'black']
   for i in range(5):
       start_index = i*12
       end_index = (i+1)*12
       subset = unrate[start_index:end_index]
       plt.plot(subset['MONTH'], subset['VALUE'], c=colors[i])
       
   plt.show()
   

   运行结果：
   

5. legend

   fig = plt.figure(figsize=(10,6))
   colors = ['red', 'blue', 'green', 'orange', 'black']
   for i in range(5):
       start_index = i*12
       end_index = (i+1)*12
       subset = unrate[start_index:end_index]
       label = str(1948 + i)
       plt.plot(subset['MONTH'], subset['VALUE'], c=colors[i], label=label)
   plt.legend(loc='best')
   #print help(plt.legend)
   plt.show()
   

   运行结果：
   

6. plt.legend(loc=‘upper left’)
   运行结果：