How to plot bar graphs with same X coordinates side by side ('dodged')

Question

import matplotlib.pyplot as plt

gridnumber = range(1,4)

b1 = plt.bar(gridnumber, [0.2, 0.3, 0.1], width=0.4,
                label=\"Bar 1\", align=\"center\")

b2         


        

Answer 1

Here are two examples of creating a side-by-side bar chart when you have more than two "categories" in a group.

Manual Method

Manually set the position and width of each bar.

import numpy as np
import matplotlib.pyplot as plt
from matplotlib import ticker

coins = ['penny', 'nickle', 'dime', 'quarter']
worth = np.array([.01, .05, .10, .25])

# Coin values times *n* coins
#    This controls how many bars we get in each group
values = [worth*i for i in range(1,6)]

n = len(values)                # Number of bars to plot
w = .15                        # With of each column
x = np.arange(0, len(coins))   # Center position of group on x axis

for i, value in enumerate(values):
    position = x + (w*(1-n)/2) + i*w
    plt.bar(position, value, width=w, label=f'{i+1}x')

plt.xticks(x, coins);

plt.ylabel('Monetary Value')
plt.gca().yaxis.set_major_formatter(ticker.FormatStrFormatter('$%.2f'))

plt.legend()

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Pandas Method

If you put the data into a pandas DataFrame, pandas will do the hard stuff for you.

import pandas as pd
coins = ['penny', 'nickle', 'dime', 'quarter']
worth = [0.01, 0.05, 0.10, 0.25]
df = pd.DataFrame(worth, columns=['1x'], index=coins)
df['2x'] = df['1x'] * 2 
df['3x'] = df['1x'] * 3 
df['4x'] = df['1x'] * 4 
df['5x'] = df['1x'] * 5 

from matplotlib import ticker
import matplotlib.pyplot as plt

df.plot(kind='bar')

plt.ylabel('Monetary Value')
plt.gca().yaxis.set_major_formatter(ticker.FormatStrFormatter('$%.2f'))
plt.gca().xaxis.set_tick_params(rotation=0)

Pandas creates a similar figure...