How Do I Use Quiver In Python For Polar?

Firstly, yes I have read previous threads and documentation about this issue, for example How to make a quiver plot in polar coordinates. This didn't help me all the way. Let me sh

Solution 1:

The only real problem with your code was a numpy problem, i.e. in your dr has the wrong dimensions. With slight adjustments to your code:

from matplotlib import pyplot as plt
import numpy as np

#to make the code runnable
u_sol = [1]
alpha0 = 5*np.pi/180
alpha = 10*np.pi/180

radii = np.linspace(0.2,1,10)
print(radii)
thetas = np.linspace(alpha0-alpha,alpha0+alpha,20)
print(thetas)
theta, r = np.meshgrid(thetas, radii)

q = 0.0001


#dr = [-q/x for x in radii]*u_sol[0]
dr = -q/r
dt = 0

f = plt.figure()
ax = f.add_subplot(111, polar=True)

ax.quiver(
    theta, r,
    dr * np.cos(theta) - dt * np.sin(theta),
    dr * np.sin(theta) + dt * np.cos(theta),
)

plt.show()

I get the following image:

Note that in the radii definition, I moved the lower limit from 0.1 to 0.2 as otherwise the arrows get so long that they point to the other side of the origin, which looks quite weird.