matplotlib.pyplot.plot() 如何连接散点？

Question

When we use pyplot.plot(x, y) in matplotlib, a line plot, which connects all the points (vertices), is drawn by default. I want to understand, exactly how does plot() do this? How does it connect the points? Does it use something like Bresenham's Line algorithm to accomplish this?

Answer 1

Matplotlib doesn't do anything more than connect the points in the order they were given

You pass two arrays with x and y coordinates. Matplotlib takes the first point (x1,y1) and draws a line to the second pair (x2,y2), then from the second pair to the third and so on until the last pair

x = [1,2,3]
y = [1,5,2]
plt.plot(x,y, 'ro-')

Answer 2

If I plot two points, I get a list containing one Line object

In [58]: g=plt.gca()                                                                           
In [59]: g                                                                                     
Out[59]: <matplotlib.axes._subplots.AxesSubplot at 0x7fce94a26400>
In [60]: g.plot([0,1],[1,2])                                                                   
Out[60]: [<matplotlib.lines.Line2D at 0x7fce94a26160>]

https://matplotlib.org/api/_as_gen/matplotlib.lines.Line2D.html#matplotlib.lines.Line2D

That in turn has many attributes and methods, though a particularly relevant one appears to be a Path object

In [67]: aline._path                                                                           
Out[67]: 
Path(array([[0., 1.],
       [1., 2.]]), None)
In [68]: aline._path.__dict__                                                                  
Out[68]: 
{'_vertices': array([[0., 1.],
        [1., 2.]]),
 '_codes': None,
 '_interpolation_steps': 1,
 '_simplify_threshold': 0.1111111111111111,
 '_should_simplify': False,
 '_has_nonfinite': False,
 '_readonly': False}

https://matplotlib.org/api/path_api.html#matplotlib.path.Path

Note its code types includes pen drawing directions like: move to and line to . Graphics backends often take commands like: "put the pen at x", "draw line to y", "lift pen". The backend takes care of interpolating the points between x and y, not the commanding code. In that case the edge is not accessible to you.

While it doesn't use matplotlib , you might find the turtle graphics package instructive. That lets you command a drawing pen directly.

https://docs.python.org/3/library/turtle.html