Bug summary

I have a decreasing function $y\colon [1,3600] \to \mathbb{R}^+$.
I try to set the logarithmic scale for the y-axis, but if the range of the function is small (i.e., the initial and final value are closeby), then the logarithmic scale does not work and it only prints the linear scale.

Code for reproduction

import random

import matplotlib.pyplot as plt


T = 3600
n = 1000
y_start = 10**4
y_end = 0.9*y_start

random.seed(42)
# Generate n increasing random values between 1 and T
x = [random.randrange(1, T) for _ in range(n)]
x.sort()
# Generate n decreasing random values between y_start and y_end
y = [random.uniform(y_end, y_start) for _ in x]

y.sort(reverse=True)

fig, ax = plt.subplots()
ax.set_yscale('log')
ax.plot(x, y)

plt.savefig('step_function.pdf')

Actual outcome

step_function.pdf

Expected outcome

I expected the logarithmis scale. In this example it happens if you set y_end = 0.2*y_start

step_function.pdf

Additional information

No response

Operating system

Linux debian 6.10.11+bpo-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.10.11-1~bpo12+1 (2024-10-03) x86_64 GNU/Linux

Matplotlib Version

3.10.0

Matplotlib Backend

qtagg

Python version

Python 3.13.0

Jupyter version

No response

Installation

conda