Change Marker Size in Matplotlib

Matplotlib is a popular plotting library for Python that allows users to create various types of plots, including scatter plots, line plots, bar plots, and more. One important aspect of creating plots in Matplotlib is customizing the appearance of markers, such as changing their size. In this article, we will explore how to change the marker size in Matplotlib.

Scatter Plot with Custom Marker Size

The scatter function in Matplotlib is used to create scatter plots. We can customize the marker size by specifying the s parameter, which controls the marker size. Here is an example of creating a scatter plot with custom marker size:

import matplotlib.pyplot as plt

# Data
x = [1, 2, 3, 4, 5]
y = [2, 3, 4, 5, 6]
sizes = [20, 50, 80, 110, 140]

plt.scatter(x, y, s=sizes)
plt.show()

Output:

In this example, we have set the marker sizes to [20, 50, 80, 110, 140] for each data point.

Set Default Marker Size

If you want to change the default marker size for all scatter plots in a Matplotlib session, you can use the rcParams configuration. Here is an example of setting the default marker size to 100:

import matplotlib.pyplot as plt
import matplotlib as mpl

# Set default marker size
mpl.rcParams['lines.markersize'] = 100

# Data
x = [1, 2, 3, 4, 5]
y = [2, 3, 4, 5, 6]

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

Output:

Now, all the scatter plots in this session will have a default marker size of 100.

Change Marker Size Dynamically

You can also change the marker size based on a condition or a variable. Here is an example of changing the marker size dynamically based on the value of a variable sizes:

import matplotlib.pyplot as plt

# Data
x = [1, 2, 3, 4, 5]
y = [2, 3, 4, 5, 6]
sizes = [20, 50, 80, 110, 140]

plt.scatter(x, y, s=sizes)
plt.show()

Output:

In this example, the marker size for each point will be determined by the corresponding value in the sizes list.

Bubble Chart

A bubble chart is a variation of a scatter plot where the marker size represents a third dimension, in addition to the x and y coordinates. Here is an example of creating a bubble chart in Matplotlib:

import matplotlib.pyplot as plt

# Data
x = [1, 2, 3, 4, 5]
y = [2, 3, 4, 5, 6]
sizes = [20, 50, 80, 110, 140]

plt.scatter(x, y, s=sizes)
plt.show()

Output:

In this example, the marker size represents a third dimension of the data.

Customize Marker Size in Other Plot Types

Apart from scatter plots, you can also customize marker size in other plot types, such as line plots and bar plots. Here is an example of changing marker size in a line plot:

import matplotlib.pyplot as plt

# Data
x = [1, 2, 3, 4, 5]
y = [2, 3, 4, 5, 6]

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

Output:

In this example, we have set the marker size to 10 for the data points in the line plot.