Matplotlib:在对数图中绘制垂直箭头 [英] Matplotlib: Draw a vertical arrow in a log-log plot

问题描述

我无法在以下 log-log 图中绘制简单的垂直箭头:

I am not able to draw a simple, vertical arrow in the following log-log plot:

#!/usr/bin/python2

import matplotlib.pyplot as plt
import matplotlib as mpl

plt.yscale('log')
plt.xscale('log')
plt.ylim((1e-20,1e-10))
plt.xlim((1e-12,1))

plt.arrow(0.00006666, 1e-20, 0, 1e-8 - 1e-20, length_includes_head=True)

plt.savefig('test.pdf')

它只是不显示.在文档中，似乎所有参数(如宽度，高度等)都与轴的比例有关.这是非常违反直觉的.我尝试使用axisartist包的twin()在我的顶部定义一个轴，限制(0,1),(0,1)可以更好地控制箭头的参数，但是我无法弄清楚如何在主要轴的顶部拥有一个完全独立的轴.

It just doesn't show. From the documentation it appears as if all the arguments, like width, height and so on relate to the scale of the axis. This is very counter-intuitive. I tried using twin() of the axisartist package to define an axis on top of mine with limits (0,1), (0,1) to have more control over the arrow's parameters, but I couldn't figure out how to have a completely independent axis on top of the primary one.

有什么想法吗?

推荐答案

子图方法

创建子图后，请执行以下操作

After creating the subplots do the following

• 对齐位置
• 使用 set_axis_off() 关闭轴(刻度、标签等)
• 画箭头！

• Align the positions
• Use set_axis_off() to turn the axis off (ticks, labels, etc)
• Draw the arrow!

那么几行就能得到您想要的东西！

So a few lines gets whats you want!

例如

#!/usr/bin/python2

import matplotlib.pyplot as plt

hax = plt.subplot(1,2,1)
plt.yscale('log')
plt.xscale('log')
plt.ylim((1e-20,1e-10))
plt.xlim((1e-12,1))

hax2 = plt.subplot(1,2,2)
plt.arrow(0.1, 1, 0, 1, length_includes_head=True)

hax.set_position([0.1, 0.1, 0.8, 0.8])
hax2.set_position([0.1, 0.1, 0.8, 0.8])

hax2.set_axis_off()

plt.savefig('test.pdf')

重新调整数据

虽然轴标签可能很棘手，但另一种可能更容易的方法是重新缩放数据.

Alternatively a possibly easier approach, though the axis labels may be tricky, is to rescale the data.

即

import numpy 

# Other import commands and data input

plt.plot(numpy.log10(x), numpy.log10(y))) 

这不是一个很好的解决方案，但如果您可以处理刻度标签，那就是一个不错的结果！

Not a great solution, but a decent result if you can handle the tick labels!

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