Python 使用 matplotlib 绘制水平线
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Plot a horizontal line using matplotlib
提问by Ibe
I have used spline interpolation to smooth a time series and would also like to add a horizontal line to the plot. But there seems to be an issue that is out of my grips. Any assistance would be really helpful. Here is what I have:
我已经使用样条插值来平滑时间序列，并且还想在图中添加一条水平线。但似乎有一个问题超出了我的掌握。任何帮助都会非常有帮助。这是我所拥有的：
annual = np.arange(1,21,1)
l = np.array(value_list) # a list with 20 values
spl = UnivariateSpline(annual,l)
xs = np.linspace(1,21,200)
plt.plot(xs,spl(xs),'b')
plt.plot([0,len(xs)],[40,40],'r--',lw=2)
pylab.ylim([0,200])
plt.show()
problem seems to be with my use of [0,len(xs)]for horizontal line plotting.
问题似乎与我[0,len(xs)]对水平线绘图的使用有关。
采纳答案by chill_turner
You are correct, I think the [0,len(xs)]is throwing you off. You'll want to reuse the original x-axis variable xsand plot that with another numpy array of the same length that has your variable in it.
你是对的，我认为这[0,len(xs)]会让你失望。您需要重用原始的 x 轴变量，xs并用另一个长度相同的 numpy 数组绘制它，其中包含您的变量。
annual = np.arange(1,21,1)
l = np.array(value_list) # a list with 20 values
spl = UnivariateSpline(annual,l)
xs = np.linspace(1,21,200)
plt.plot(xs,spl(xs),'b')
#####horizontal line
horiz_line_data = np.array([40 for i in xrange(len(xs))])
plt.plot(xs, horiz_line_data, 'r--')
###########plt.plot([0,len(xs)],[40,40],'r--',lw=2)
pylab.ylim([0,200])
plt.show()
Hopefully that fixes the problem!
希望能解决问题！
回答by BlivetWidget
回答by MosteM
A nice and easy way for those people who always forget the command axhlineis the following
对于那些总是忘记命令的人来说，一个简单而简单的方法axhline是以下
plt.plot(x, [y]*len(x))
In your case xs = xand y = 40.
If len(x) is large, then this becomes inefficient and you should really use axhline.
在你的情况xs = x和y = 40. 如果 len(x) 很大，那么这会变得效率低下，您应该真正使用axhline.
回答by jdhao
If you want to draw a horizontal line in the axes, you might also try ax.hlines()method. You need to specify yposition and xminand xmaxin the data coordinate (i.e, your actual data range in the x-axis). A sample code snippet is:
如果你想在轴上画一条水平线，你也可以尝试ax.hlines()方法。您需要在数据坐标（即 x 轴中的实际数据范围）中指定y位置和xmin和xmax。示例代码片段是：
import matplotlib.pyplot as plt
import numpy as np
x = np.linspace(1, 21, 200)
y = np.exp(-x)
fig, ax = plt.subplots()
ax.plot(x, y)
ax.hlines(y=0.2, xmin=4, xmax=20, linewidth=2, color='r')
plt.show()
The snippet above will plot a horizontal line in the axes at y=0.2. The horizontal line starts at x=4and ends at x=20. The generated image is:
上面的代码片段将在坐标区中绘制一条水平线y=0.2。水平线从 开始到x=4结束x=20。生成的图像是：
回答by ayorgo
In addition to the most upvoted answer here, one can also chain axhlineafter calling ploton a pandas's DataFrame.
除了这里最受好评的答案外，您还可以axhline在调用plota 后链接pandas's DataFrame。
import pandas as pd
(pd.DataFrame([1, 2, 3])
.plot(kind='bar', color='orange')
.axhline(y=1.5));
回答by Mehdi
You can use plt.gridto draw a horizontal line.
可以plt.grid用来画一条水平线。
import numpy as np
from matplotlib import pyplot as plt
from scipy.interpolate import UnivariateSpline
from matplotlib.ticker import LinearLocator
# your data here
annual = np.arange(1,21,1)
l = np.random.random(20)
spl = UnivariateSpline(annual,l)
xs = np.linspace(1,21,200)
# plot your data
plt.plot(xs,spl(xs),'b')
# horizental line?
ax = plt.axes()
# three ticks:
ax.yaxis.set_major_locator(LinearLocator(3))
# plot grids only on y axis on major locations
plt.grid(True, which='major', axis='y')
# show
plt.show()
回答by Trenton McKinney
Use matplotlib.pyplot.hlines
用 matplotlib.pyplot.hlines
import numpy as np
import matplotlib.pyplot as plt
xs = np.linspace(1, 21, 200)
plt.hlines(y=40, xmin=0, xmax=len(xs), colors='r', linestyles='--', lw=2)
plt.show()
