Changing Line Colors of a Rectangle

Introduction

In this lab, we will learn how to change the colors of lines intersecting a rectangle using the .intersects_bbox function from Matplotlib. We will create a rectangle and generate random lines that intersect it. Then, we will change the color of the intersecting lines to red and the remaining lines to blue.

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Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL matplotlib(("`Matplotlib`")) -.-> matplotlib/BasicConceptsGroup(["`Basic Concepts`"]) matplotlib(("`Matplotlib`")) -.-> matplotlib/PlottingDataGroup(["`Plotting Data`"]) python(("`Python`")) -.-> python/ControlFlowGroup(["`Control Flow`"]) python(("`Python`")) -.-> python/DataStructuresGroup(["`Data Structures`"]) python(("`Python`")) -.-> python/ModulesandPackagesGroup(["`Modules and Packages`"]) python(("`Python`")) -.-> python/PythonStandardLibraryGroup(["`Python Standard Library`"]) python(("`Python`")) -.-> python/DataScienceandMachineLearningGroup(["`Data Science and Machine Learning`"]) python(("`Python`")) -.-> python/FunctionsGroup(["`Functions`"]) matplotlib/BasicConceptsGroup -.-> matplotlib/importing_matplotlib("`Importing Matplotlib`") matplotlib/BasicConceptsGroup -.-> matplotlib/figures_axes("`Understanding Figures and Axes`") matplotlib/PlottingDataGroup -.-> matplotlib/line_plots("`Line Plots`") python/ControlFlowGroup -.-> python/conditional_statements("`Conditional Statements`") python/ControlFlowGroup -.-> python/for_loops("`For Loops`") python/DataStructuresGroup -.-> python/lists("`Lists`") python/DataStructuresGroup -.-> python/tuples("`Tuples`") python/ModulesandPackagesGroup -.-> python/importing_modules("`Importing Modules`") python/ModulesandPackagesGroup -.-> python/standard_libraries("`Common Standard Libraries`") python/PythonStandardLibraryGroup -.-> python/math_random("`Math and Random`") python/DataScienceandMachineLearningGroup -.-> python/numerical_computing("`Numerical Computing`") python/DataScienceandMachineLearningGroup -.-> python/data_visualization("`Data Visualization`") python/FunctionsGroup -.-> python/build_in_functions("`Build-in Functions`") subgraph Lab Skills matplotlib/importing_matplotlib -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} matplotlib/figures_axes -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} matplotlib/line_plots -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/conditional_statements -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/for_loops -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/lists -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/tuples -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/importing_modules -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/standard_libraries -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/math_random -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/numerical_computing -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/data_visualization -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} python/build_in_functions -.-> lab-48585{{"`Changing Line Colors of a Rectangle`"}} end

Import the required libraries

We will import matplotlib.pyplot and numpy libraries to create the rectangle and generate random lines.

import matplotlib.pyplot as plt
import numpy as np

Set up the rectangle

We will define the position and dimensions of the rectangle using left, bottom, width, and height variables. Then, we will create the rectangle using Rectangle class and add it to the plot using add_patch method.

left, bottom, width, height = (-1, -1, 2, 2)
rect = plt.Rectangle((left, bottom), width, height,
                     facecolor="black", alpha=0.1)

fig, ax = plt.subplots()
ax.add_patch(rect)

Generate random lines

We will generate 12 random lines using numpy library and plot them using plot method. If a line intersects the rectangle, its color will be red, otherwise blue. We will use Path class to create a line and intersects_bbox method to check if it intersects the rectangle.

bbox = Bbox.from_bounds(left, bottom, width, height)

for i in range(12):
    vertices = (np.random.random((2, 2)) - 0.5) * 6.0
    path = Path(vertices)
    if path.intersects_bbox(bbox):
        color = 'r'
    else:
        color = 'b'
    ax.plot(vertices[:, 0], vertices[:, 1], color=color)

Display the plot

We will display the plot using show method.

plt.show()

Summary

In this lab, we learned how to change the colors of lines intersecting a rectangle using the .intersects_bbox function from Matplotlib. We created a rectangle and generated random lines that intersected it. Then, we changed the color of the intersecting lines to red and the remaining lines to blue.