在python中绘制一个螺旋，其中r = theta ^ 2为0 <= theta <= 10 * pi ...

Question

so my question is how to make a polar plot r = f(theta) for a function f by calculating r for a range of values of theta and then converting r and theta to Cartesian coordinates using equations x = r cos(theta) , y = r sin(theta) .

BUT I need to plot the spiral r = (theta)^2 for 0 <= theta <= 10*pi this is what I have so far....not getting a spiral here.

#! /usr/bin/env python

import matplotlib.pyplot as plt
from math import cos, sin, pi
from numpy import linspace

for theta in linspace(0,10*pi):
        r = ((theta)**2)
        x = r*cos(theta)
        y = r*sin(theta)


plt.plot(x,y)  
plt.savefig("spiral.png")
plt.show()

Answer 1

You need to create a list of values, not just a single point. In your case, you keep calculating x and y , but never save them anywhere. So all you are plotting is the pair (x,y) after the last iteration.

x = []
y = []
for theta in linspace(0,10*pi):
    r = ((theta)**2)
    x.append(r*cos(theta))
    y.append(r*sin(theta))

plt.plot(x,y)  
plt.show()

Output

Answer 2

import numpy as np
import matplotlib.pyplot as plt

theta = np.radians(np.linspace(0,360*5,1000))
r = theta**2
x_2 = r*np.cos(theta)
y_2 = r*np.sin(theta)
plt.figure(figsize=[10,10])
plt.plot(x_2,y_2)
plt.show()