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Nyquist plot with imaginary poles, semi-circles only working after 'trick' #613

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@kevindekemele

I'm plotting the Nyquist diagram of a transfer function which has poles on the imaginary axis:


import control
import matplotlib.pyplot as plt
import numpy as np

K = 1

Gp =  control.tf([1], [1,1,0,0,0]) 
Gc = control.tf([K], [1]) 


control.nyquist_plot(Gp*Gc,plot=True,omega_num=1000)
plt.show()

Which results in the following incorrect plot, that does not show infinte semicircles, but something incorrect:
image

Also using indent_direction and indent_radius did not solve this.
The trick I found that makes it work is if I add omega_limits=[0.001,10000] to nyquist_plot:

image

Can you please fix such that the incorrect 'line' does not appear?

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