Plot the distribution of salaries in baseball leagues over time

baseball_salaries_violin_plots.py

# Long version with full comments

# We want to plot the distribution of salaries in baseball leagues over time

import pandas as pd
import numpy as np
import seaborn as sns
import matplotlib.pyplot as plt

# Download a dataset from Lahman's database of baseball statistics 
# with the salaries of baseball players, over the years from 1985 until 2016, 
# together with the team of the player, and the league in which the team is playing.
df = pd.read_csv("https://raw.githubusercontent.com/chadwickbureau/baseballdatabank/master/core/Salaries.csv")

# Just making the headers friendlier/readable
rename_dict = {"yearID": "Year", "teamID": "Team", "lgID": "League", "playerID": "Player", "salary": "Salary"}
df.rename(rename_dict, axis='columns', inplace=True) 

# Create one figure, with just one subplot (figure is the overall thing, ax corresponds to the individual plot[s] )
fig, ax = plt.subplots()
# Increase the size of the plot
fig.set_size_inches(20, 4)

# Add a horizontal grid line
ax.grid(which='major', color='gray', linewidth=0.25, alpha=0.5)


# Remove salaries of zero (so that we can take the log), and a couple of outliers (that is just for beautification)
# Specifically, we remove the following entries:
# 6179	1993	NYA	AL	jamesdi01	0
# 6194	1993	NYA	AL	silveda01	10900
# 6659	1994	CHA	AL	carych01	50000
# 9679	1997	FLO	NL	penaal01	50000
# 12007	1999	PIT	NL	martija02	0
df = df[df.Salary > 50000]

# Take the log of the salary so that we can plot the distribution of the logSalary over time
# (Alternatively, we can make the y-axis below to be log-scaled)
df['logSalary'] = np.log10(df.Salary)

# Plot the distribution of salaries over time using Violin plots.
# We put the year on the x-axis, and we plot the distribution across the y-axis
# We also use a "split" violin plot and we plot one side the distribution for NL and on the other side the AL
sns.violinplot(
    data=df,
    x='Year',
    y='logSalary',
    color='orange',
    hue='League',
    split=True,
    ax=ax)

fig.savefig('baseball.png', bbox_inches='tight')