Plotting multiple radius values for single theta

Question

I am trying to plot points in a polar grid, but I don't know how to plot multiple points for a single theta value. I have a float type for theta that goes from 0 to 90 degrees split into 90 evenly spaced intervals:

import numpy as np
theta = np.linspace(0,np.pi/2,90)

And then I have a list of various r or radius values generated by the following loop:

i = 100
initialR = 0.32130341
radiusList = []
for y in range(i):
    radius = pow(1.02,y)*initialR
    radiusList.append (float(radius))

What I want is for a given theta value, say theta = pi/2 for it to plot points at every radius value. Is there a simple way to do this? I am planning on using matplotlib pyplot scatter, but don't know if there is a better option? I feel like it should be straight forward, but I haven't found any plots where the theta and r vary in size.

Yes -- just be appending to a list of theta in the same loop as you build radiusList. — Linuxios
Are you committed to using matplotlib's scatter, or will polar suffice? You may want to look at this example for making a scatter plot on a polar coordinate system. — Rory Daulton
I don't want to append to the list of theta, that would just give me a really long list. Can you please clarify? @Linuxios — summer
@RoryDaulton yes, I have looked at that example already. I think my issue is that I just don't know how to get my data in the proper format so theta and r are the same size. — summer

Diziet Asahi Diziet Asahi · Accepted Answer · 2019-08-07T21:48:47

Notice that your second block of code can be vectorized as:

np.power(1.02, np.arange(i))*initialR

It this what you are trying to get?

thetas = np.linspace(0,np.pi/2,10)
i = 100
initialR = 0.32130341
radii = np.power(1.02, np.arange(i))*initialR

fig, ax = plt.subplots(subplot_kw=dict(projection='polar'))
for theta in thetas:
    plt.plot(np.full(radii.shape, theta), radii)

EDIT: drawing single points instead of a line:

thetas = np.linspace(0,np.pi/2,10)
i = 100
initialR = 0.32130341
radii = np.power(1.02, np.arange(i))*initialR

fig, ax = plt.subplots(subplot_kw=dict(projection='polar'))
for theta in thetas:
    plt.plot(np.full(radii.shape, theta), radii, 'o', mfc='none')

Plotting multiple radius values for single theta

1 Answers