mvoelske mvoelske -4 years ago 201
Python Question

Matplotlib: draw lines with width given in data coordinates

I'm trying to figure out how to draw lines with widths in data units. For example, in the following code snippet, I would want the horizontal part of the line of width 80 to always extend from the y=-40 to the y=+40 mark, and stay that way even if the limits of the coordinate system change. Is there a way to achieve this with Line2D objects in matplotlib? Any other way to get a similar effect?

from pylab import figure, gca, Line2D

figure()
ax = gca()
ax.set_xlim(-50, 50)
ax.set_ylim(-75, 75)

ax.add_line(Line2D([-50, 0, 50], [-50, 0, 0], linewidth=80))

ax.grid()


line width in screen coordinates

Answer Source

You could use fill_between:

import matplotlib.pyplot as plt
import numpy as np

fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.set_xlim(-50, 50)
ax.set_ylim(-75, 75)
x = [-50, 0, 50]
y = np.array([-50, 0, 0])

ax.fill_between(x,y-30,y+30)

ax.grid()
plt.show()

yields

enter image description here

but unlike the line generated by

ax.add_line(Line2D([-50, 0, 50], [-50, 0, 0], linewidth=80))

the vertical thickness of the line will always be constant in data coordinates.

See also link to documentation.

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