Question

I am a beginner with Numpy/Matplotlib (and scientific python) and I find that very easy things are relatively complicated to do because they have to be done by hand. (like without having this awesome math environment)

I thought that at least there would be a possibility for example to easy get the angle of two intersecting lines.

I want to do the following. I have those three points:

 (q)  |
  \   |
   \  |
    \a|
     \|
     (p)
      |
      |
      |
     (o)

1. All what I want to do is to calculate the angle a.
2. Also later I want to get a point z which is relative to the origin (0,0) with the distance from p to q and the angle a.

The first thing is easy with math, first I calculate two vectors a1 and a2.
Then I calculate:

a = arccos( ( a1 * a2 ) / (|a1| * |a2|) )

and so on…

But how the hell do I do this in matplotlib?

Is there a way to “just” give the three points and it does everything?
I don’t really see a advantage of doing this whole stuff on my own with having an math environment.

Answer 1

Numpy provides the same functionality math provides but working on both numbers and arrays. So you would do :

import numpy as np

a = np.arccos((a1 * a2) / (np.abs(a1) * np.abs(a2)))