hyg_scatter.py

# -*- coding: utf-8 -*-
"""
Exploring star mapping

Author: Aaron Penne
Created: 03/15/2018
Developed with Python 3.6 on Windows 10
"""

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import imageio
import os

#np.random.seed(1138)

min_mag = -20
max_mag = 20
vis_mag = 8
steps = 40
twinkles = 10

# Set output directory, make it if needed
output_dir = os.path.relpath('output')  # Windows machine
if not os.path.isdir(output_dir):
    os.mkdir(output_dir)

# Get input file
input_file = os.path.join('data', 'hygdata_v3.csv')
df = pd.read_csv(input_file)    

# Filter to certain magnitudes, ignore the sun
df = df[df.mag > min_mag]
df = df[df.mag < max_mag]

# Filter the size/alpha of each marker by magnitude bin (log scale)
mag = {}
for i,value in enumerate(np.geomspace(abs(min_mag), abs(min_mag)+max_mag, num=steps)):
    mag[i] = (df['mag'] >= (value + min_mag)) & (df['mag'] < vis_mag)
marker = {}
for i,value in enumerate(np.geomspace(4, 0.1, num=steps)):
    marker[i] = value
alpha = {}
for i,value in enumerate(np.geomspace(1, 0.4, num=steps)):
    alpha[i] = value
    


# Workaround to get each magnitude bin only plotted once
mag_xor = {}
for i in range(len(mag)):
    if i == len(mag)-1:
        mag_xor[i] = mag[i]
        break
    mag_xor[i] = mag[i] & (mag[i] ^ mag[i+1])
mag = mag_xor




# Plot with varying alphas to get twinkle effect
for i in range(twinkles):
    
    # Set up plot
    fig, ax = plt.subplots(figsize=(10, 5), dpi=150)
    
    # Black out the entire background
    fig.set_facecolor('black')
    ax.set_facecolor('black')
    
    # Plot each star, differing parameters depending on magnitude
    for j in range(steps):
        x = df.loc[mag[j], 'ra']
        y = df.loc[mag[j], 'dec']
        plt.plot(x, y, 
                 color='white', 
                 linestyle='none',
                 linewidth=0,
                 marker='.', 
                 markersize=marker[j],
                 alpha=alpha[j],
                 markeredgewidth=0)
        
    # Twinkle hack because other methods failed. Just plot random black patches.
    x = np.random.uniform(0, 24, (1,300))
    y = np.random.uniform(-90, 90, (1,300))
    
    print(x[0][0], y[0][0])
    
    plt.plot(x, y, 
         color='black', 
         linestyle='none',
         linewidth=0,
         marker='.', 
         markersize=3,
         alpha=0.5,
         markeredgewidth=0)

    ## Why not make constellations pop? Doesn't look as good
    #x = df.loc[df['bf'].notnull(), 'ra']
    #y = df.loc[df['bf'].notnull(), 'dec']
    #plt.plot(x, y, 
    #         color='white', 
    #         linestyle='none',
    #         linewidth=0,
    #         marker='.', 
    #         markersize=5,
    #         alpha=1,
    #         markeredgewidth=0)
    
    # Despine plot
    for side in ['right', 'left', 'top', 'bottom']:
        ax.spines[side].set_visible(False)
        
    # Set axis ticks/labels
    plt.xticks(np.linspace(0, 24, 5), 
               family='monospace',
               size=5,
               color='white', 
               alpha=0.15)
    plt.yticks(np.linspace(-90, 90, 5),
               family='monospace',
               size=5,
               color='white', 
               alpha=0.15)
    plt.text(0, -105,
             'Right Ascension (hours)',
             family='monospace',
             size=5,
             color='white', 
             alpha=0.15,
             horizontalalignment='left')
    plt.text(-1.2, -51,
             'Declination (degrees)',
             family='monospace',
             size=5,
             color='white', 
             alpha=0.15,
             horizontalalignment='left',
             rotation='vertical')
    
    # Set max/min axis limits
    plt.ylim([-90, 90])
    plt.xlim([0, 24])
    
    # Add text
    plt.text(0, 115, 'The Night Sky',
             family='monospace',
             size=12,
             horizontalalignment='left',
             weight='bold',
             color='white',
             alpha=0.8)
    plt.text(0, 111, 'Equirectangular projection of stars (mag<8)'.format(vis_mag),
             family='monospace',
             size=7,
             horizontalalignment='left',
             verticalalignment='top',
             weight='bold',
             color='white',
             alpha=0.5)
    plt.text(24, -120, '© 2018 Aaron Penne\nData: HYG Stellar Database\n\nApparent magnitude scale is logarithmic\nBrighter stars have a smaller apparent magnitude',
             family='monospace',
             size=7,
             horizontalalignment='right',
             verticalalignment='top',
             weight='bold',
             color='white',
             alpha=0.5)
    

    # Save plot
    fig.savefig(os.path.join(output_dir, 'hyg_scatter_{:02}.png'.format(i)),
                dpi=fig.dpi,
                facecolor=fig.get_facecolor(),
                edgecolor='none',
                bbox_inches='tight',
                pad_inches=0.5)

    plt.close(fig)
    
    
## Append images to create GIF 
# Read in all png files in folder - https://stackoverflow.com/a/27593246
png_files = [f for f in os.listdir(output_dir) if f.endswith('.png')]

charts = []
# Append all the charts
for f in png_files:
    charts.append(imageio.imread(os.path.join(output_dir, f)))


# Save gif
imageio.mimsave(os.path.join(output_dir, 'hyg_scatter_twinkle.gif'), charts, format='GIF', duration=0.01)