python – x轴matplotlib上的良好日期格式

Time    test
0:05    2
0:06    2
0:07    2
0:08    2
0:09    2
0:10    2
0:11    2

该数据帧从0:00开始,到11:59结束.我创建了以下图表：

x = dftestgraph['Time']
y = dftestgraph['test']
plt.ylabel('Number of tasks')
plt.plot(x, y, color="#00a1e4", label="Number of Tasks")
plt.fill(x, y, '#00a1e4', alpha=0.8)
plt.show()

为什么图表底部有一条线,将我填充的图形分成两半？我想将我的x轴格式化为(0：00,0：30,1：00等)我试过：

plt.xticks(0:00, 11:59, 30:00))

但是这不起作用.
我的问题是：

>为什么我的图表中有一行,我该如何解决？
>如何以正确的格式设置x轴？

我在下面汇总了一个MWE,展示了它是如何完成的.它还显示了一种格式化xaxis标签的方法,它来自以下帖子：Creating graph with date and time in axis labels with matplotlib和Plotting time in Python with Matplotlib.

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

plt.close('all')

#---- generate some data ----

t = [datetime.datetime(2015, 1, 1, 0) + 
     datetime.timedelta(hours=i) for i in np.arange(0,12.1,0.5)]
x = np.random.rand(len(t))

#---- create figure and axe ----

fig = plt.figure()

ax = fig.add_axes([0.1, 0.2, 0.85, 0.75])

#---- format xaxis ----

# position of the labels
xtk_loc = [datetime.datetime(2015, 1, 1, 0) + 
           datetime.timedelta(hours=i) for i in np.arange(0,12.1,0.5)]
ax.set_xticks(xtk_loc)
ax.tick_params(axis='both', direction='out', top='off', right='off')

# format of the labels
hfmt = dates.DateFormatter('%H:%M')
ax.xaxis.set_major_formatter(hfmt)
fig.autofmt_xdate(rotation=90, ha='center')

#---- set axes labels ----

ax.set_ylabel('Number of tasks', labelpad=10, fontsize=14)
ax.set_xlabel('Time', labelpad=20, fontsize=14)

#---- plot data ----

ax.plot(t, x, color="#004c99", label="Number of Tasks")
ax.fill_between(t, x, 0, facecolor='#00a1e4', alpha=0.5, lw=0.5)

#---- set axis limits ----

timemin = datetime.datetime(2015, 1, 1, 0)
timemax = datetime.datetime(2015, 1, 1, 12)

ax.axis(xmin=timemin, xmax=timemax)

plt.show()  

这导致：