Set Marker Size of Scatter Plot in Matplotlib

Suraj Joshi Apr 12, 2021 Apr 24, 2020 Matplotlib Matplotlib Scatter

s Keyword Argument to Set Matplotlib Scatter Marker Size
Set the Same Scatter Marker Size of All Points in Matplotlib
Increase Scatter Marker Size of Points Non-Uniformly in Matplotlib
markersize Parameter to Set Scatter Marker Size in Matplotlib plot Function

Set Marker Size of Scatter Plot in Matplotlib

The size of scatter markers in Matplotlib is specified by the s keyword argument of the function scatter(), where s is a scalar or an array.

`s` Keyword Argument to Set Matplotlib Scatter Marker Size

The Syntax of the scatter function:

matplotlib.pyplot.scatter(x, y,
                          s=None,
                          c='b', 
                          marker='o', 
                          cmap=None, 
                          norm=None,
                          vmin=None, 
                          vmax=None, 
                          alpha=None, 
                          linewidths=None,
                          faceted=True, 
                          verts=None,
                          hold=None, 
                          **kwargs)

Where, s is a scalar or an array of the same length as x and y, to set the scatter marker size. The default scatter marker size is rcParams['lines.markersize'] ** 2. According to documentation, s is the marker size in points².

Set the Same Scatter Marker Size of All Points in Matplotlib

import numpy as np
import matplotlib.pyplot as plt

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

plt.scatter(x,y,s=500,c='magenta')

plt.title('Scatter plot of sinx')
plt.xlabel('x')
plt.ylabel('sinx')
plt.xlim(0,6)
plt.ylim(-2,2)
plt.show()

Increased markersize of scatter plot uniformly

Increase Scatter Marker Size of Points Non-Uniformly in Matplotlib

Double the Width of Matplotlib Scatter Marker

To double the width (or height) of the marker we need to increase s by a factor of 4 as A = W*H => (2W)*(2H)= 4A.

import matplotlib.pyplot as plt
x = [1,2,3,4,5]
y = [a**2 for a in x]
s = [10*4**n for n in range(len(x))]
plt.scatter(x,y,s=s)
plt.title('Doubling width of marker in scatter plot')
plt.xlabel('x')
plt.ylabel('x**2')
plt.xlim(0,6)
plt.ylim(0,30)
plt.show()

doubled width of markers

Double the Area of Matplotlib Scatter Marker

To double the area of the marker, we increase the area by a factor of 2, so the marker size scales linearly with the area.

import matplotlib.pyplot as plt
x = [1,2,3,4,5]
y = [a**2 for a in x]
s = [10*2**n for n in range(len(x))]
plt.scatter(x,y,s=s)
plt.title('Doubling area of marker in scatter plot')
plt.xlabel('x')
plt.ylabel('x**2')
plt.xlim(0,6)
plt.ylim(0,30)
plt.show()

doubled area of markers

`markersize` Parameter to Set Scatter Marker Size in Matplotlib `plot` Function

import matplotlib.pyplot as plt

x = [1,2,3,4,5]
y = [0]*len(x)

plt.plot(x,y, 'bo', markersize=10)  
plt.show()

Here the area of the circle is controlled by the markersize parameter.

markersize parameter to control size in plot method

Author: Suraj Joshi

Suraj Joshi is a backend software engineer at Matrice.ai.

s Keyword Argument to Set Matplotlib Scatter Marker Size