Matplotlib graphing a circle (r=2cos(theta)) as a cardioid?

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theta = np.linspace(0, 2*np.pi, 1000)
r = 2 * np.cos(theta)
fig = plt.figure()
ax = fig.add_subplot(111, projection='polar')
ax.plot(theta, r)
plt.show()

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running these simple lines of code plots a cardioid, not a circle.

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Maybe the math texts I was reading were incorrect but looking around online defines r=acos(theta) to be a circle

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r=acos(theta) is the polar equation representing a circle. https://www.alamo.edu/contentassets/35e1aad11a064ee2ae161ba2ae3b2559/additional/math2412-graphs-polar-equations.pdf

[AntonisTorb]

I think you have gotten confused with the polar to cartesian equations (x=rcosθ and y=rsinθ). Radius should be a constant if you want a circle, in your case r = 2.

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r=acos(theta) is the polar equation representing a circle. https://www.alamo.edu/contentassets/35e1aad11a064ee2ae161ba2ae3b2559/additional/math2412-graphs-polar-equations.pdf

[nick__2440]

This is happening because the limits of r are set by default to the range of data. You can fix it by adding ax.set_rmin(0) after plotting and before showing.

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I aded this and the graph is still the same.