[matplotlib]How to Create a Bar Plot in Python

This article shows how to create a bar plot in matplotlib.

How to create a bar plot

In the beginning, I show how to create a bar plot.

Matplotlib provides methods for drawing a bar plot.

The way to use of "matplotlib.pyplot.bar" is described in matplotlib documentation.

matplotlib documentation

This is the example code to create a bar plot using "matplotlib.pyplot.bar".

import numpy as np
import matplotlib.pyplot as plt
 
x = np.array([1, 2, 3, 4, 5])
y = np.array([10, 20, 30, 40, 50])


plt.bar(x, y)

plt.show()

The above code generates the following graph.

> plt.bar(x, y)

The variables "x" and "y" are data lists for bar plot generation.

Example of adding graph elements to a bar plot

I show example of adding axis labels, legends etc. to a bar plot.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt
 
x = np.array([1, 2, 3, 4, 5])
y = np.array([10, 20, 30, 40, 50])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x, y, label='bar')

plt.legend()

plt.show()

The above code generates the following graph.

> fig = plt.figure(figsize = (5,5), facecolor='lightblue')

A figure object is created.

> plt.xlabel('X')
> plt.ylabel('Y')

Axis labels are added.

The following article explains how to set axis elements.

How to Set Axis Elements[Label, Range, Ticks]

> plt.bar(x, y, label='bar')

The "label=" argument is used to specify the legend string.

The following article explains how to add legend.

How to Add Legend

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How to Set Bar Width

I show how to set bar width.

You can change bar width by specifying "width=" as an argument.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt
 
x = np.array([1, 2, 3, 4, 5])
y = np.array([10, 20, 30, 40, 50])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x, y, label='bar', width=0.1)

plt.legend()

plt.show()

The above code generates the following graph.

◆width=0.1

◆width=1

> plt.bar(x, y, label='bar', width=0.1)

The bar width is changed by specifying the argument "width="

How to Set Bar Color

I show how to set bar color.

You can change bar color by specifying "color=" as an argument.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt
 
x = np.array([1, 2, 3, 4, 5])
y = np.array([10, 20, 30, 40, 50])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x, y, label='bar', width=0.8, color='GreenYellow')

plt.legend()

plt.show()

The above code generates the following graph.

> plt.bar(x, y, label='bar', width=0.8, color='GreenYellow')

The bar color is changed by specifying the argument "color="

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How to Add Edge of Bar

I show how to add edge of bar.

You can add edge of bar by specifying "edgecolor=" as an argument.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt
 
x = np.array([1, 2, 3, 4, 5])
y = np.array([10, 20, 30, 40, 50])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x, y, label='bar', width=0.8, color='GreenYellow', edgecolor='Green')

plt.legend()

plt.show()

The above code generates the following graph.

> plt.bar(x, y, label='bar', width=0.8, color='GreenYellow', edgecolor='Green')

The color of bar edge is changed by specifying the argument "edgecolor="

How to Set Edge Width of Bar Plot

I show how to set edge width of bar plot.

You can set edge width by specifying "linewidth=" as an argument.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt
 
x = np.array([1, 2, 3, 4, 5])
y = np.array([10, 20, 30, 40, 50])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x, y, label='bar', width=0.8, color='GreenYellow', edgecolor='Green', linewidth=5)

plt.legend()

plt.show()

The above code generates the following graph.

> plt.bar(x, y, label='bar', width=0.8, color='GreenYellow', edgecolor='Green', linewidth=5)

The edge width is changed by specifying the argument "linewidth="

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How to Plot Multiple Bar Plots

I show how to plot multiple bar plots.

To plot the two bars side by side, the x-axis elements are shifted by half its width.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt


width_bar = 0.4

x = np.array([1, 2, 3, 4, 5])
x1 = x - width_bar/2
x2 = x + width_bar/2

y1 = np.array([10, 20, 30, 40, 50])
y2 = np.array([10, 15, 10, 15, 10])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x1, y1, label='y1', width=width_bar, align="center")
plt.bar(x2, y2, label='y2', width=width_bar, align="center")

plt.legend()

plt.show()

The above code generates the following graph.

> x = np.array([1, 2, 3, 4, 5])
> x1 = x - width_bar/2
> x2 = x + width_bar/2

The x-axis elements are shifted by half its width.

> plt.bar(x1, y1, label='y1', width=width_bar, align="center")
> plt.bar(x2, y2, label='y2', width=width_bar, align="center")

Two bar plots are plotted.

How to Create a Stacked Bar Plot

I show how to create a stacked bar plot.

You can create a stacked bar plot by specifying "bottom=" as an argument.

This is the example code.

import numpy as np
import matplotlib.pyplot as plt


width_bar = 0.8

x = np.array([1, 2, 3, 4, 5])

y1 = np.array([10, 20, 30, 40, 50])
y2 = np.array([10, 15, 10, 15, 10])


fig = plt.figure(figsize = (5,5), facecolor='lightblue')

plt.xlabel('X')
plt.ylabel('Y')

plt.bar(x, y1, label='y1', width=width_bar, align="center")
plt.bar(x, y2, label='y2', width=width_bar, align="center",bottom=y1)

plt.legend()

plt.show()

The above code generates the following graph.

> plt.bar(x, y1, label='y1', width=width_bar, align="center")
> plt.bar(x, y2, label='y2', width=width_bar, align="center",bottom=y1

By specifying "bottom=y1", The bar "y2" can be stacked on top of the bar "y1".

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