Matplotlib y 轴值未排序[重复]

问题描述：

我正在尝试使用 matplotlib 进行绘图。绘图显示 Y 轴无序的问题。

这是代码。

# -*- coding: UTF-8 -*-
import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import datetime
import numpy as np
I020 = [ line.strip('
').split(",") for line in 
open(r'D:Usersa0476Anaconda3TickDataPV5sdata1.csv')][1:]
Time = [ datetime.datetime.strptime(line[0],"%H%M%S%f") for line in I020 ]
Time1 = [ mdates.date2num(line) for line in Time ]
Solar = [ line[1] for line in I020 ]
order = np.argsort(Time1)
xs = np.array(Time1)[order]
ys = np.array(Solar)[order]
plt.title('Solar data')
plt.xlabel('Time')
plt.ylabel('Solar')
ax.plot_date(xs, ys, 'k-')
hfmt = mdates.DateFormatter('%H:%M:%S')
ax.xaxis.set_major_formatter(hfmt)
plt.show()

CSV 数据

time        solar
7000000     50.35
8000000     41.01
9000000     69.16
10000000    94.5
11000000    111.9
12000000    103
13000000    98.6
14000000    36.45
15000000    34.74
16000000    34.17
17000000    34.6

解决方案 1：

发生这种情况的原因是因为您的数据被绘制为字符串。

解决方案是将 y 轴数据转换为浮点数。只需在列表推导中将其转换为浮点数即可：

Solar = [float(line[1]) for line in I020]

我还建议在使用日期/时间时使用 matplotlib 的 x 轴自动格式化。这将旋转标签等，使图表看起来更好：

plt.gcf().autofmt_xdate()

你的例子变成：

I020 = [ line.strip('
').split(",") for line in open('PV5sdata1.csv')][1:]
Time = [datetime.datetime.strptime(line[0],"%H%M%S%f") for line in I020]
Time1 = [mdates.date2num(line) for line in Time]
Solar = [float(line[1]) for line in I020]

xs = np.array(Time1)  # You don't really need to do this but I've left it in
ys = np.array(Solar)

fig, ax = plt.subplots() # using matplotlib's Object Oriented API

ax.set_title('Solar data')
ax.set_xlabel('Time')
ax.set_ylabel('Solar')
ax.plot_date(xs, ys, 'k-')

hfmt = mdates.DateFormatter('%H:%M:%S')
ax.xaxis.set_major_formatter(hfmt)
plt.gcf().autofmt_xdate()

plt.show()

得出：