Matplotlib Text Rotation

Introduction

In this lab, you will learn how to rotate text in Matplotlib using the rotation_mode parameter. The rotation_mode parameter determines the order of rotation and alignment of the text. There are two modes available: default and anchor.

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Import the necessary libraries

First, we need to import the necessary libraries. In this lab, we will use Matplotlib to create the plots.

import matplotlib.pyplot as plt

Define the test_rotation_mode function

We will create a function called test_rotation_mode that will create subplots to test the different rotation modes. It takes two parameters: fig and mode.

def test_rotation_mode(fig, mode):

Define the horizontal and vertical alignment lists

Next, we will define the horizontal and vertical alignment lists that will be used to create the subplots. We will create three elements for each list: "left", "center", and "right" for horizontal alignment, and "top", "center", and "bottom" for vertical alignment.

ha_list = ["left", "center", "right"]
va_list = ["top", "center", "baseline", "bottom"]

Create the subplots

Now, we will create the subplots using the subplots function. We will create a grid of subplots with the same aspect ratio, and we will remove the ticks from the x and y axes. We will also add a vertical and horizontal line at the center of each subplot to help visualize the alignment.

axs = fig.subplots(len(va_list), len(ha_list), sharex=True, sharey=True,
                   subplot_kw=dict(aspect=1),
                   gridspec_kw=dict(hspace=0, wspace=0))

for i, va in enumerate(va_list):
    for j, ha in enumerate(ha_list):
        ax = axs[i, j]
        ax.set(xticks=[], yticks=[])
        ax.axvline(0.5, color="skyblue", zorder=0)
        ax.axhline(0.5, color="skyblue", zorder=0)
        ax.plot(0.5, 0.5, color="C0", marker="o", zorder=1)

Add text to the subplots

We will add text to each subplot using the text function. We will use the parameters rotation, horizontalalignment, verticalalignment, and rotation_mode to rotate and align the text. We will also use the bbox parameter to highlight the bounding box of the text.

kw = (
    {} if mode == "default" else
    {"bbox": dict(boxstyle="square,pad=0.", ec="none", fc="C1", alpha=0.3)}
)

texts = {}

for i, va in enumerate(va_list):
    for j, ha in enumerate(ha_list):
        ax = axs[i, j]
        tx = ax.text(0.5, 0.5, "Tpg",
                     size="x-large", rotation=40,
                     horizontalalignment=ha, verticalalignment=va,
                     rotation_mode=mode, **kw)
        texts[ax] = tx

Highlight the bounding box of the text

If the rotation_mode is set to 'default', we will highlight the bounding box of the text using a rectangle. We will use the get_window_extent function to get the bounding box and transform it to the data coordinates using the transData attribute.

if mode == "default":
    fig.canvas.draw()
    for ax, text in texts.items():
        bb = text.get_window_extent().transformed(ax.transData.inverted())
        rect = plt.Rectangle((bb.x0, bb.y0), bb.width, bb.height,
                             facecolor="C1", alpha=0.3, zorder=2)
        ax.add_patch(rect)

Create the subfigures and call the test_rotation_mode function

We will create two subfigures and call the test_rotation_mode function with the fig and mode parameters.

fig = plt.figure(figsize=(8, 5))
subfigs = fig.subfigures(1, 2)
test_rotation_mode(subfigs[0], "default")
test_rotation_mode(subfigs[1], "anchor")
plt.show()

Summary

In this lab, we learned how to rotate text in Matplotlib using the rotation_mode parameter. We created a function called test_rotation_mode that created subplots to test the different rotation modes. We defined the horizontal and vertical alignment lists, created the subplots, added text to the subplots, and highlighted the bounding box of the text. Finally, we created the subfigures and called the test_rotation_mode function.