Python中的 Matplotlib.dates.datestr2num()

Matplotlib是Python中用于数组二维图的惊人可视化库。 Matplotlib 是一个基于 NumPy 数组构建的多平台数据可视化库，旨在与更广泛的 SciPy 堆栈配合使用。

matplotlib.dates.datestr2num()

matplotlib.dates.datestr2num()函数用于通过使用dateutil.parser.parser()将日期字符串转换为 datenum。

Syntax: matplotlib.dates.datestr2num(d, default=None)

Parameters:

1. d: It is a string or a sequence of strings representing the dates.
2. default: This is an optional parameter that is a datetime instance. This is used when fields are not present in d, as a default.

示例 1：

from datetime import datetime
import matplotlib.pyplot as plt
from matplotlib.dates import (
    DateFormatter, AutoDateLocator, AutoDateFormatter, datestr2num
)
  
  
days = [
    '30/01/2019',
    '31/01/2019', 
    '01/02/2019',
    '02/02/2019', 
    '03/02/2019', 
    '04/02/2019'
]
data1 = [2, 5, 13, 6, 11, 7]
data2 = [6, 3, 10, 3, 6, 5]
  
z = datestr2num([
    datetime.strptime(day, '%d/%m/%Y').strftime('%m/%d/%Y')
    for day in days
])
  
r = 0.25
  
figure = plt.figure(figsize =(8, 4))
axes = figure.add_subplot(111)
  
axes.bar(z - r, data1, width = 2 * r,
         color ='g', align ='center',
         tick_label = day)
  
axes.bar(z + r, data2, width = 2 * r,
         color ='y', align ='center', 
         tick_label = day)
  
axes.xaxis_date()
axes.xaxis.set_major_locator(
    AutoDateLocator(minticks = 3, interval_multiples = False))
  
axes.xaxis.set_major_formatter(DateFormatter("%d/%m/%y"))
  
plt.show()

输出：

示例 2：

import matplotlib
import matplotlib.pyplot as plt
import matplotlib.dates
  
  
dates =  ['1920-05-06', 
          '1920-05-07', 
          '1947-05-08', 
          '1920-05-09']
  
converted_dates = matplotlib.dates.datestr2num(dates)
  
x_axis = (converted_dates)
y_axis = range(0, 4)
  
plt.plot_date( x_axis, y_axis, '-' )
  
plt.show()

输出：