5 Best Ways to Insert a Newline in Matplotlib Labels with TeX in Python

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πŸ’‘ Problem Formulation: When using Matplotlib with TeX for typesetting mathematical expressions within plot labels, adding a newline can pose a challenge. Users often require multi-line labels to improve readability or to convey complex information. This article demonstrates how to achieve this, transforming an input such as ax.set_title("This is an $ax^2 + bx + c$ equation") into a desired output where the equation is on a new line below the text “This is an”.

Method 1: Explicit Newline with \\\\ in TeX Strings

The method involves adding the TeX newline character \\\\ directly into the label string. This is particularly useful when you are writing raw TeX code in your labels. The double backslash is necessary because in LaTeX, a single backslash is used for commands.

Here’s an example:

import matplotlib.pyplot as plt

plt.figure()
plt.title(r"This is an\\$ax^2 + bx + c$ equation")
plt.show()

Output: A plot with the title “This is an” on the first line and the equation “ax^2 + bx + c” on the second line.

This code snippet uses a raw string (indicated by the r prefix) to prevent Python from interpreting the backslashes as escape characters. The \\\\ is interpreted by TeX as a newline, thus splitting the title into two lines.

Method 2: Using textwrap to Automate Line Breaks

If you have a long label and want to wrap the text to a new line automatically, the Python textwrap module can be used. This is especially handy when working with dynamically generated text where manual insertion of line breaks is unfeasible.

Here’s an example:

import matplotlib.pyplot as plt
import textwrap

label = "This is an $ax^2 + bx + c$ equation"
wrapped_label = textwrap.fill(label, width=20)

plt.figure()
plt.title(wrapped_label)
plt.show()

Output: A plot with a title automatically wrapped every 20 characters, putting part of the equation on the second line.

The textwrap.fill function automatically adds newlines to fit the label within a specified width of character columns. When rendered by Matplotlib, the title is accordingly split into multiple lines.

Method 3: Using Matplotlib’s set_title with Keyword Arguments

Matplotlib’s set_title method accepts keyword arguments that can be utilized to manipulate text properties. This includes the ability to set the space between lines in a label (line spacing), effectively creating a multi-line label.

Here’s an example:

import matplotlib.pyplot as plt

plt.figure()
plt.title("This is an\n$ax^2 + bx + c$ equation", linespacing=2)
plt.show()

Output: A plot with a title where “This is an” and “ax^2 + bx + c” appear on separate lines with increased spacing.

This method uses the simple newline character (\n) in the string to start a new line of text. The linespacing argument then adjusts the space between the generated lines.

Method 4: Using plt.text() for Advanced Positioning

The plt.text() allows for advanced text positioning, using coordinates for placing individual text elements. This gives you fine control over the layout of your text labels on the plot.

Here’s an example:

import matplotlib.pyplot as plt

plt.figure()
plt.text(0.5, 0.9, "This is an", ha='center', va='center', transform=plt.gca().transAxes)
plt.text(0.5, 0.8, "$ax^2 + bx + c$", ha='center', va='center', transform=plt.gca().transAxes)
plt.show()

Output: A plot with “This is an” precisely positioned above the equation “ax^2 + bx + c”.

This code places two separate text elements at specified axes-relative coordinates. The `ha` and `va` arguments stand for horizontal and vertical alignment, respectively, ensuring that the text is centered.

Bonus One-Liner Method 5: Using Python’s Triple Quotes

Python’s triple quotes can be used to write multi-line strings directly. This can be a quick and handy way to format multiline text in Matplotlib without additional processing.

Here’s an example:

import matplotlib.pyplot as plt

plt.figure()
plt.title("""This is an
$ax^2 + bx + c$ equation""")
plt.show()

Output: A plot with the title spread over two lines, “This is an” followed by the equation “ax^2 + bx + c”.

By using triple quotes, any newlines entered within the string are directly interpreted as actual newlines in the output, making it a convenient one-liner method for quick plotting tasks.

Summary/Discussion

  • Method 1: Explicit Newline with \\\\. Direct and clear for TeX users. Requires knowledge of TeX syntax.
  • Method 2: Using textwrap. Automated and ideal for dynamic text. Could lead to awkward breaks in mathematical expressions.
  • Method 3: Matplotlib’s set_title Method. Simple and quick. Limited formatting control compared to other methods.
  • Method 4: Using plt.text(). Most flexible for layout. Requires manual positioning which can be complex for dynamic or complex layouts.
  • Bonus Method 5: Python’s Triple Quotes. Easiest for quick tasks. Not suitable for complex formatting or large amounts of text.