Multiple images in subplot grid in Matplotlib - Time & Space Complexity

Time Complexity: Multiple images in subplot grid

O(n)

Understanding Time Complexity

When showing many images in a grid using matplotlib, we want to know how the time to draw grows as we add more images.

We ask: How does adding more images affect the total work matplotlib does?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

import matplotlib.pyplot as plt
import numpy as np

fig, axes = plt.subplots(3, 3)
for i, ax in enumerate(axes.flat):
    img = np.random.rand(10, 10)
    ax.imshow(img)
plt.show()

This code creates a 3 by 3 grid of images, each showing a small random 10x10 picture.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Loop over each subplot to draw an image.
• How many times: Once for each image in the grid (rows x columns).

How Execution Grows With Input

As we add more images, the work grows roughly in direct proportion to the number of images.

Input Size (n images)	Approx. Operations
9 (3x3)	9 image draws
100 (10x10)	100 image draws
1024 (32x32)	1024 image draws

Pattern observation: Doubling the number of images roughly doubles the work.

Final Time Complexity

Time Complexity: O(n)

This means the time to draw grows linearly with the number of images shown.

Common Mistake

[X] Wrong: "Adding more images won't affect time much because each image is small."

[OK] Correct: Even small images require drawing work, so more images add up and increase total time.

Interview Connect

Understanding how drawing many images scales helps you explain performance in data visualization tasks clearly and confidently.

Self-Check

"What if we changed the image size from 10x10 to 100x100 pixels? How would the time complexity change?"