Lecture 27 – Visualizing Two Numerical Variables¶

Data 94, Spring 2021¶

from datascience import *
import numpy as np
Table.interactive_plots()

Our first dataset today comes from Basketball Reference. It contains per-game averages of players in the 2019-2020 NBA season.

Run the cell below to load it in, select the relevant columns, and do some data cleaning.

Note: Most of the interesting data comes from the "better" players in the league; we will only look at players who averaged at least 10 points per game in the season. This isn't perfect, since there were plenty of good players who averaged less than 10 points per game.

nba = Table.read_table('data/nba-2020.csv') \
           .select('Player', 'Pos', 'Tm', 'PTS', 'TRB', 'AST', '3PA', '3P%') \
           .where('3PA', are.not_equal_to(0))

def remove_code(name):
    return name[:name.index('\\')]

def get_court(pos):
    if 'G' in pos:
        return 'Guard'
    else:
        return 'Forward'

nba = nba.with_columns('Player', nba.apply(remove_code, 'Player'),
                       'Pos', nba.apply(get_court, 'Pos')) \
         .where('PTS', are.above(10))

nba

A description of each column:

'Player': name
'Pos': general position (either Forward or Guard)
'Tm': abbreviated team
'PTS': average number of points scored per game
'TRB': average number of rebounds per game (a player receives a rebound when they grab the ball after someone misses)
'AST': average number of assists per game (a player receives an assist when they pass the ball to someone who then scores)
'3PA': average number of three-point shots attempted per game (a three point shot is one from behind a certain line, which is between 22-24 feet from the basket)
'3P%': average proportion of three-point shots that go in

Review – bar charts and histograms¶

Bar charts¶

nba.group('Pos', np.mean).select('Pos', 'PTS mean', 'TRB mean', 'AST mean')

nba.group('Pos', np.mean).select('Pos', 'PTS mean', 'TRB mean', 'AST mean').barh('Pos')

Player	Pos	Tm	PTS	TRB	AST	3PA	3P%
Bam Adebayo	Forward	MIA	15.9	10.2	5.1	0.2	0.143
LaMarcus Aldridge	Forward	SAS	18.9	7.4	2.4	3	0.389
Jarrett Allen	Forward	BRK	11.1	9.6	1.6	0.1	0
Giannis Antetokounmpo	Forward	MIL	29.5	13.6	5.6	4.7	0.304
Carmelo Anthony	Forward	POR	15.4	6.3	1.5	3.9	0.385
OG Anunoby	Forward	TOR	10.6	5.3	1.6	3.3	0.39
D.J. Augustin	Guard	ORL	10.5	2.1	4.6	3.5	0.348
Deandre Ayton	Forward	PHO	18.2	11.5	1.9	0.3	0.231
Marvin Bagley III	Forward	SAC	14.2	7.5	0.8	1.7	0.182
Lonzo Ball	Guard	NOP	11.8	6.1	7	6.3	0.375

Pos	PTS mean	TRB mean	AST mean
Forward	15.6297	6.68901	2.41099
Guard	16.7463	4.00244	4.45244