Matplotlib Scatter plots in Python

In this article we will show you how to create scatter charts in Python using matplotlib

Syntax

matplotlib.pyplot.scatter(x, y, s=None, c=None, marker=None, cmap=None, norm=None, vmin=None, vmax=None, alpha=None, linewidths=None, *, edgecolors=None, plotnonfinite=False, data=None, **kwargs)

parameters:

• x_axis_data- An array containing x-axis data
• y_axis_data- An array containing y-axis data
• s- marker size (can be scalar or array of size equal to size of x or y)
• c- color of sequence of colors for markers
• marker– marker style, marker can be either an instance of the class or the text shorthand for a particular marker.
• cmap- A Colormap instance or registered colormap name. cmap is only used if c is an array of floats.
• linewidths- The linewidth of the marker edges. Note: The default edgecolors is ‘face'. You may want to change this as well.
• edgecolor- The edge color of the marker.
• alpha- The alpha blending value, between 0 (transparent) and 1 (opaque).

Examples

basic example

In this example we take some hypothetical golf scores and the number of players who got that score and plot them.

Lets see this in action

import matplotlib.pyplot as plot
import numpy as np

x = np.array([5,7,8,7,2,9,7,9,4,9,12,9,6])
y = np.array([65,66,67,68,69,70,71,72,73,74,75,76,77])

plot.scatter(x, y)
plot.show()

This displayed the following

scatter basic

matplotlib Scatter chart titles

In this matplotlib scatter plot example, we used the xlabel, ylabel, and title functions to show X-Axis, Y-Axis labels, and chart titles.

import matplotlib.pyplot as plot
import numpy as np

x = np.array([5,7,8,7,2,9,7,9,4,9,12,9,6])
y = np.array([65,66,67,68,69,70,71,72,73,74,75,76,77])

plot.title('Golf Scores')
plot.xlabel('Players')
plot.ylabel('Score')

plot.scatter(x, y)
plot.show()

This will display the following

scatter chart titles

matplotlib Scatter chart colors

You can set your own color for each scatter plot with the color or the c argument

Here is an example

import matplotlib.pyplot as plot
import numpy as np

x = np.array([5,7,8,7,2,9,7,9,4,9,12,9,6])
y = np.array([65,66,67,68,69,70,71,72,73,74,75,76,77])

plot.title('Golf Scores')
plot.xlabel('Players')
plot.ylabel('Score')
plot.scatter(x, y, color = 'green')
plot.show()

You will see this

matplotlib Scatter chart Color Each Dot

You can even set a specific color for each dot by using an array of colors as value for the c argument

Here is an example

import matplotlib.pyplot as plot
import numpy as np

x = np.array([5,7,8,7,2,9,7,9,4,9,12,9,6])
y = np.array([65,66,67,68,69,70,71,72,73,74,75,76,77])
colors = np.array(["red","green","blue","yellow","pink","black","orange","purple","beige","brown","gray","cyan","magenta"])

plot.title('Golf Scores')
plot.xlabel('Players')
plot.ylabel('Score')
plot.scatter(x, y, c=colors)
plot.show()

This displays the following

matplotlib Scatter chart using a colormap

We can use a colormap. A colormap is basically a list of colors, where each color has a value that ranges from 0 to 100.

Here is an example

import matplotlib.pyplot as plot
import numpy as np

x = np.array([5,7,8,7,2,9,7,9,4,9,12,9,6])
y = np.array([65,66,67,68,69,70,71,72,73,74,75,76,77])
colors = np.array([0, 10, 20, 30, 40, 45, 50, 55, 60, 70, 80, 90, 100])

plot.title('Golf Scores')
plot.xlabel('Players')
plot.ylabel('Score')
plot.scatter(x, y, c=colors, cmap='rainbow')
plot.show()

This displayed the following

Changing the size of the dots

You can change the size of the dots with the s argument.

You need to make sure the array for sizes has the same length as the arrays for the x- and y-axis

Here is an example

import matplotlib.pyplot as plot
import numpy as np

x = np.array([5,7,8,7,2,9,7,9,4,9,12,9,6])
y = np.array([65,66,67,68,69,70,71,72,73,74,75,76,77])
sizes = np.array([90,500,100,200,50,70,60,20,10,300,600,800,1000])

plot.title('Golf Scores')
plot.xlabel('Players')
plot.ylabel('Score')
plot.scatter(x, y, s=sizes)
plot.show()

This displayed the following

Random colors and sizes

In this example we will now show random colors and examples with random data

import matplotlib.pyplot as plot
import numpy as np

x = np.random.randint(50, size=(50))
y = np.random.randint(50, size=(50))
colors = np.random.randint(50, size=(50))
sizes = 10 * np.random.randint(50, size=(50))

plot.title('Scatter chart example')
plot.xlabel('X Axis')
plot.ylabel('Y Axis')

plot.scatter(x, y, c=colors, s=sizes, alpha=0.5, cmap='rainbow')

plot.colorbar()

plot.show() 

This displayed the following

Links

github code examples

matplotlib documentation