我想要实现的目标

Question

我正在尝试在我的天气数据图中格式化x轴。我对y轴感到满意，但是我所有尝试将x轴变成一个体面的，人类可读的格式到目前为止都无法正常工作。经过几个小时的反复试验，我希望得到你的帮助。

我想要实现的目标

最后，我希望每30分钟有一个刻度线，每小时有一个垂直虚线网格线，下面标有HH：MM，另外每天晚上00:00写入日期。这样的事情（谨慎，前面的ASCII艺术不好！）：

     :         :         :
     :         :         :
     :         :         :
     :         :         :
     :         :         :
|====|====|====|====|====|====|====
   23:00     00:00     01:00
            09JAN18

所有时间都是UTC，这将是最终的豪华版本。但我的问题早就开始了。

我的代码段

首先，我尝试将其变为可读格式。我想出了

locator = mdates.AutoDateLocator()
plt.gca().xaxis.set_major_locator(locator)
plt.gca().xaxis.set_major_formatter(mdates.AutoDateFormatter(locator))

希望我能摆脱exp

结果

输出并不是我所希望的：

pi@raspi3b:~/wx-logging $ python plot.py
[( 15.94,  57.86,  992.65,  1019.99, 1515460740)
 ( 15.96,  57.8 ,  992.65,  1019.99, 1515460745)
 ( 15.99,  57.79,  992.68,  1020.02, 1515460750) ...,
 ( 13.25,  55.7 ,  990.16,  1017.43, 1515496060)
 ( 13.31,  56.  ,  990.14,  1017.41, 1515496065)
 ( 13.34,  56.32,  990.13,  1017.4 , 1515496070)]
Traceback (most recent call last):
  File "plot.py", line 123, in <module>
    plt.savefig("plot.png", dpi=150)
  File "/usr/lib/python2.7/dist-packages/matplotlib/pyplot.py", line 697, in savefig
    res = fig.savefig(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/matplotlib/figure.py", line 1572, in savefig
    self.canvas.print_figure(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/matplotlib/backend_bases.py", line 2244, in print_figure
    **kwargs)
  File "/usr/lib/python2.7/dist-packages/matplotlib/backends/backend_agg.py", line 545, in print_png
    FigureCanvasAgg.draw(self)
  File "/usr/lib/python2.7/dist-packages/matplotlib/backends/backend_agg.py", line 464, in draw
    self.figure.draw(self.renderer)
  File "/usr/lib/python2.7/dist-packages/matplotlib/artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/matplotlib/figure.py", line 1143, in draw
    renderer, self, dsu, self.suppressComposite)
  File "/usr/lib/python2.7/dist-packages/matplotlib/image.py", line 139, in _draw_list_compositing_images
    a.draw(renderer)
  File "/usr/lib/python2.7/dist-packages/mpl_toolkits/axes_grid1/parasite_axes.py", line 295, in draw
    self._get_base_axes_attr("draw")(self, renderer)
  File "/usr/lib/python2.7/dist-packages/mpl_toolkits/axisartist/axislines.py", line 778, in draw
    super(Axes, self).draw(renderer, inframe)
  File "/usr/lib/python2.7/dist-packages/matplotlib/artist.py", line 63, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/matplotlib/axes/_base.py", line 2409, in draw
    mimage._draw_list_compositing_images(renderer, self, dsu)
  File "/usr/lib/python2.7/dist-packages/matplotlib/image.py", line 139, in _draw_list_compositing_images
    a.draw(renderer)
  File "/usr/lib/python2.7/dist-packages/mpl_toolkits/axisartist/axis_artist.py", line 915, in draw
    gl = self._grid_helper.get_gridlines(self._which, self._axis)
  File "/usr/lib/python2.7/dist-packages/mpl_toolkits/axisartist/axislines.py", line 546, in get_gridlines
    locs.extend(self.axes.xaxis.major.locator())
  File "/usr/lib/python2.7/dist-packages/matplotlib/dates.py", line 983, in __call__
    self.refresh()
  File "/usr/lib/python2.7/dist-packages/matplotlib/dates.py", line 1003, in refresh
    dmin, dmax = self.viewlim_to_dt()
  File "/usr/lib/python2.7/dist-packages/matplotlib/dates.py", line 760, in viewlim_to_dt
    return num2date(vmin, self.tz), num2date(vmax, self.tz)
  File "/usr/lib/python2.7/dist-packages/matplotlib/dates.py", line 401, in num2date
    return _from_ordinalf(x, tz)
  File "/usr/lib/python2.7/dist-packages/matplotlib/dates.py", line 254, in _from_ordinalf
    dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)
ValueError: year is out of range
pi@raspi3b:~/wx-logging $

不完全有希望。我无法弄清楚为什么它会说ValueError: year is out of range因为它是一个unix纪元时间戳。

我做错了什么？如何实现上述期望的结果？我真的很感激在正确的方向上轻推。谢谢你的帮助！

一切顺利，克里斯

完整的脚本

到目前为止，为了给你一些上下文我的完整脚本。

#!/usr/bin/python
# -*- coding: utf-8 -*-

import matplotlib
matplotlib.use('AGG')
from mpl_toolkits.axes_grid1 import host_subplot
import mpl_toolkits.axisartist as aa
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
from matplotlib.ticker import FuncFormatter
import numpy as np
from numpy import vectorize
import datetime
import shutil
import math

# Dewpoint calculation
def dewpoint(tempC, rlHum):

    r  = 8314.3
    mw = 18.016

    if tempC >= 0:
        a = 7.5
        b = 237.3
    # over water:
    # elif tempC < 0:
    #     a = 7.6
    #     b = 240.7
    #
    # over ice:
    elif tempC < 0:
        a = 9.5
        b = 265.5

    saettDampfDruck = 6.1078 * 10**((a*tempC)/(b+tempC))
    dampfDruck = rlHum / 100.0 * saettDampfDruck
    v = math.log10(dampfDruck/6.1078)
    dewpC = b*v/(a-v)

    return dewpC

# translate cm into inches
def cm2inch(*tupl):
    inch = 2.54
    if isinstance(tupl[0], tuple):
        return tuple(i/inch for i in tupl[0])
    else:
        return tuple(i/inch for i in tupl)

vdewpoint = vectorize(dewpoint)

convertDate = lambda x: datetime.datetime.utcfromtimestamp(x)

data = np.genfromtxt('/home/pi/wx-logging/wx-log2.txt', 
                    delimiter=';', 
                    usecols=(1, 2, 3, 5, 6), 
                    names=['temp', 'humidity', 'press', 'slp', 'time'], 
                    converters={'6': convertDate}, 
                    dtype='float, float, float, float, int')

print data

plt.figure(figsize=cm2inch(29.7, 21))

host = host_subplot(111, axes_class=aa.Axes)
plt.subplots_adjust(right=0.75)
par1 = host.twinx()
par2 = host.twinx()

offset = 70 # offset of detached axis
new_fixed_axis = par2.get_grid_helper().new_fixed_axis
par2.axis["right"] = par2.get_grid_helper().new_fixed_axis(loc="right", 
                                                            axes=par2, 
                                                            offset=(offset, 0))

par1.axis["right"].toggle(all=True)
par2.axis["right"].toggle(all=True)

host.set_title("Weather Station")
host.set_xlabel("Time")
host.set_ylabel("Temperature & Dewpoint [" + u'\u00b0'+ "C]")
par1.set_ylabel("Sealevel Pressure [hPa]")
par2.set_ylabel("relative Humidity [%]")

host.set_ylim([-20, 40]) # temperature range -20C ... +40C
par1.set_ylim([980, 1040]) # slp range 980hPa ... 1040hPa
par2.set_ylim([0, 100]) # percent


p1, = host.plot(data['time'],
                data['temp'],
                label="Temperature",
                color="red",
                linewidth=2)
p2, = host.plot(data['time'],
                vdewpoint(data['temp'],
                data['humidity']),
                label="Dewpoint",
                color="salmon",
                linewidth=0.75)
p3, = par1.plot(data['time'],
                data['slp'],
                label="Sealevel Pressure",
                color="blue",
                linewidth=0.75)
p4, = par2.plot(data['time'],
                data['humidity'],
                label="rel. Humidity",
                color="grey",
                linewidth=0.5)

locator = mdates.AutoDateLocator()
plt.gca().xaxis.set_major_locator(locator)
plt.gca().xaxis.set_major_formatter(mdates.AutoDateFormatter(locator))


plt.legend(bbox_to_anchor=(0.05, 0.05), 
           loc=3,
           ncol=2, 
           borderaxespad=0.)

plt.savefig("plot.png", dpi=150)

shutil.copyfile('/home/pi/wx-logging/plot.png', '/var/www/html/plot.png')

EDIT1：您可以下载wx-log2.txt（~58KB）的样本数据，以便尝试使用该脚本。 tiago明确建议

Answer 1

您的代码存在一些问题。首先，使用converters={'6':中引号中的列表示永远不会应用转换函数。使用不带引号的列号：

converters={6: convertDate},

另一个问题是你需要从字符串转换为整数，否则你的日期时间转换将不起作用：

convertDate = lambda x: datetime.datetime.utcfromtimestamp(int(x))

最后，time字段的数据类型必须为numpy.datatype64（并在微秒内指定，因为这是utcfromtimestamp返回的内容）。在np.genfromtxt调用中分配数据类型的正确方法如下：

data = np.genfromtxt('wx-log2.txt',  
                     delimiter=';',
                     converters={6: convertDate},
                     usecols=(1,2,3,5,6), 
                     dtype=[('temp', 'f'), ('humidity', 'f'), ('press', 'f'), 
                            ('slp', 'f'), ('time', 'datetime64[us]')])

通过以上内容，您应该了解plt.plot_date可以理解的格式的时间。

对于日期格式，您可以通过将次要刻度标记设置为HH:MM并将主要标记设置为一年中的某一天来获得与您要实现的内容类似的内容，但我不知道每30分钟还有未标记的刻度线。

这是一个简单的示例，它具有适当的时间数组，并以与您想要的格式相似的格式绘制。为简单起见，每4小时只写刻度线，但您可以更改它。

import numpy as np
import matplotlib.dates as dates
import matplotlib.pyplot as plt 

fig, ax = plt.subplots()
idx = pd.date_range('2018-01-07', '2018-01-09', freq='10min')
# generate a time range series with 10 min intervals
idx = np.arange('2018-01-07T00', '2018-01-09T02', 10, dtype='datetime64[m]')
# some random data
y = np.sin(np.arange(idx.shape[0]) / 0.01)

ax.plot_date(idx, y, '-')

ax.xaxis.set_minor_locator(dates.HourLocator(interval=4))   # every 4 hours
ax.xaxis.set_minor_formatter(dates.DateFormatter('%H:%M'))  # hours and minutes
ax.xaxis.set_major_locator(dates.DayLocator(interval=1))    # every day
ax.xaxis.set_major_formatter(dates.DateFormatter('\n%d-%m-%Y'))

matplotlib：x轴上

我想要实现的目标

我的代码段

结果

完整的脚本

1 个答案: