使用文件数据绘制日期时间（x轴）与值（y轴）的关系图

Question

我有一个文件（.dat），里面的数据格式是：

%dd %mm %yyyy %HH %MM %SS value

这些数据是用空格分开的。我想把日期、月份、年份和时间放在x轴上，把数值放在y轴上。这个程序应该能够一直从文件中读取数据，因为我有很多文件，而且它们都很大，需要分析。

这是我最近的尝试：

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
from time import gmtime, strftime
date, time, level = np.loadtxt('my_file.txt', unpack=True, usecols = (0,1,2,3), converters={ 0,1: mdates.strpdate2num('%dd/%mm/%YY %HH:%MM')}) #read format of file
# then to plot 
plt.plot_date(x=date, y=level, fmt='%dd/%mm/%YY %HH:%MM') # fmt is changed from r- 
plt.title('title')
plt.ylabel('Waterlevel (m)')
plt.grid(True)
plt.show()

Answer 1

如果我理解你的问题没错的话，我觉得这可能是一个解决办法：

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
from datetime import datetime
import numpy as np    

# Converter function
datefunc = lambda x: mdates.date2num(datetime.strptime(x, '%d %m %Y %H %M %S'))

# Read data from 'file.dat'
dates, levels = np.genfromtxt('file.dat',    # Data to be read
                              delimiter=19,  # First column is 19 characters wide
                              converters={0: datefunc}, # Formatting of column 0
                              dtype=float,   # All values are floats
                              unpack=True)   # Unpack to several variables

fig = plt.figure()
ax = fig.add_subplot(111)

# Configure x-ticks
ax.set_xticks(dates) # Tickmark + label at every plotted point
ax.xaxis.set_major_formatter(mdates.DateFormatter('%d/%m/%Y %H:%M'))

ax.plot_date(dates, levels, ls='-', marker='o')
ax.set_title('title')
ax.set_ylabel('Waterlevel (m)')
ax.grid(True)

# Format the x-axis for dates (label formatting, rotation)
fig.autofmt_xdate(rotation=45)
fig.tight_layout()

fig.show()

假设 file.dat 的内容是这样的：

01 06 2013 00 00 00 24.23
02 06 2013 01 00 00 22.23
03 06 2013 02 00 00 21.43
04 06 2013 03 00 00 24.32
04 06 2013 14 30 00 23.42
06 06 2013 03 00 00 24.32
07 06 2013 19 20 00 23.54
08 06 2013 03 00 00 26.23
08 06 2013 19 00 00 24.43
10 06 2013 12 40 00 23.22

最后的结果会变成这样：