Set Marker Size of Scatter Plot in Matplotlib

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

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()

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()

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()

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.

Related Article - Matplotlib Scatter