Question

I want to plot some values representing visible satellites into a polar graph with Python and matplotlib. I have written some code following a matplotlib example, and the polar chart is represented, but given points are not plotted:

import matplotlib
from matplotlib.pyplot import figure, show, rc, grid
from math import pi

# radar green, solid grid lines
rc('grid', color='#316931', linewidth=1, linestyle='-')
rc('xtick', labelsize=15)
rc('ytick', labelsize=15)

# force square figure and square axes looks better for polar, IMO
width, height = matplotlib.rcParams['figure.figsize']
size = min(width, height)
# make a square figure
fig = figure(figsize=(size, size))
ax = fig.add_axes([0.1, 0.1, 0.8, 0.8], polar=True, axisbg='#d5de9c')

# Satellite info [PRN, E, Az, Ss, Used (1 yes, 0 no)]
sat = [ [1, 62, 255, 46, 1],
        [14, 62, 26, 46, 1],
        [31, 42, 158, 36, 1],
        [22, 40, 76, 50, 1],
        [11, 29, 308, 0, 0],
        [19, 26, 243, 36, 1],
        [3, 13, 217, 0, 0],
        [18, 10, 93, 0, 0],
        [20, 6, 291, 0, 0],
        [5, 1, 72, 0, 0],
        [122, 43, 216, 0, 0],
        [135, 47, 203, 43, 0] ]

for index in (0, len(sat)-1):
    if(sat[index][4]>0):
        ax.plot(sat[index][2], sat[index][1], color='green', marker='s', markersize=12)
    else:
        ax.plot(sat[index][2], sat[index][1], color='gray', marker='s', markersize=12)

ax.set_rmax(2.0)
grid(True)

ax.set_title("Visible satellites", fontsize=20)
show()

What am I doing wrong?

Answer 1

Its simpler to just iterate of your list of sats like this:

for s in sat:
    if(s[4]>0):
        ax.plot(s[2], s[1],color='green', marker='s', markersize=5)
    else:
        ax.plot(s[2], s[1],color='gray', marker='s', markersize=5)

In addition to that, you’re also limiting the azimuth to <2 with the set_rmax, this leaves only 1 satellite visible, uncomment it to see all of them.

edit:
Directly unpacking the list might further improve the readability:

for (PRN, E, Az, Ss, Used) in sat:
    if(Used>0):
        ax.plot(Ss, Az,color='green', marker='s', markersize=5)
    else:
        ax.plot(Ss, Az,color='gray', marker='s', markersize=5)