Python的注释与箭一样headlength [英] Python annotation arrows with same headlength

问题描述

我使用matplotlib来创建箭头标注。

I'm using matplotlib to create annotations with arrows.

from matplotlib import pyplot as plt
plt.figure()
plt.annotate('Text1', xy=(1, 0), xytext=(1, 1), arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10))
plt.annotate('Text2', xy=(3, 0), xytext=(3, 3), arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10))
plt.annotate('Text3', xy=(6, 0), xytext=(6, 6), arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10))
plt.annotate('Text4', xy=(9, 0), xytext=(9, 9), arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10))
plt.xlim((0, 10))
plt.ylim(0, 10)
plt.show()

可以看出，箭头头的长度由行长度的影响，并且箭头之间变化。

As can be seen, the length of the arrow heads is affected by the line-length and varies between the arrows.

我在寻找一种方法来创建不同的线路长度，但平等箭箭headlengths
尽管很多选项都注释手册上列出的，我是不是能够产生期望的结果。

I'm looking for a way to create arrows with different line-lengths but equal arrow-headlengths. Although many options are listed on the annotations manual page, i was not able to produce the desired result.

作为一个替代方法，我试图用seperatedely的 plt.arrow 的绘制箭头。在这种情况下，箭头头部看上去根据需要，但使用透明度时，附加的线变得可见。

As an alternative approach i tried to plot the arrows seperatedely using plt.arrow. In that case the arrow heads looked as desired, but when using transparency, additional lines became visible.

最好的问候，zinjaai

Best regards, zinjaai

推荐答案

在 arrowprops 您不能指定头的长度，但压裂实际参数的指定为分数的箭头长度头部的长度。既然你知道 XY 和 xytext 就可以计算所需的分数为所需headlength。

In the arrowprops you can't specify the length of the head, but the frac arguement specifies the length of the head as a fraction the arrow length. Since you know xy and xytext you can compute the necessary fraction for a desired headlength.

我为您提供的例子快快行动吧（带的头长 0.5 ）。

I've don't it quickly for the example you provided (with an head length of 0.5).

from matplotlib import pyplot as plt
plt.figure()
plt.annotate('Text1', xy=(1, 0), xytext=(1, 1), 
        arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10, frac=0.5/1))
plt.annotate('Text2', xy=(3, 0), xytext=(3, 3), 
        arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10, frac=0.5/3))
plt.annotate('Text3', xy=(6, 0), xytext=(6, 6), 
        arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10, frac=0.5/6))
plt.annotate('Text4', xy=(9, 0), xytext=(9, 9), 
        arrowprops=dict(alpha=0.5, fc='r', ec='r', headwidth=10, frac=0.5/9))
plt.xlim((0, 10))
plt.ylim(0, 10)
plt.show()

结果：

您可以在一个功能，它计算箭头的长度包装这个（给 XY 和 xytext ） ，然后通过该上 plt.annotate 。

You could wrap this in a function, which computes the length of the arrow (given xy and xytext) and then passes that on to plt.annotate.

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