Matplotlibの軸目盛とフォーマッター: 読みやすいスケールを作る

import matplotlib.pyplot as plt
from matplotlib.ticker import MultipleLocator, FuncFormatter
import numpy as np
 
x = np.linspace(0, 50, 200)
y = np.log1p(x) * 3.2
 
fig, ax = plt.subplots(figsize=(7, 4))
ax.plot(x, y, color="tab:blue")
 
# xは10刻み、yは1.5刻み
ax.xaxis.set_major_locator(MultipleLocator(10))
ax.yaxis.set_major_locator(MultipleLocator(1.5))
 
# 単位付きラベル
ax.yaxis.set_major_formatter(FuncFormatter(lambda val, _: f"{val:.1f} dB"))
 
ax.set_xlabel("Samples")
ax.set_ylabel("Signal (dB)")
ax.grid(True, axis="both", linestyle="--", alpha=0.3)
plt.tight_layout()
plt.show()

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import pandas as pd
 
dates = pd.date_range("2024-01-01", periods=120, freq="D")
values = pd.Series(range(len(dates))).rolling(7, min_periods=1).mean()
 
fig, ax = plt.subplots(figsize=(8, 4))
ax.plot(dates, values, color="tab:green")
 
ax.xaxis.set_major_locator(mdates.MonthLocator(interval=1))
ax.xaxis.set_major_formatter(mdates.DateFormatter("%b %Y"))
ax.xaxis.set_minor_locator(mdates.WeekdayLocator(byweekday=mdates.MO, interval=2))
 
plt.setp(ax.get_xticklabels(), rotation=30, ha="right")
ax.set_ylabel("7-day avg")
ax.grid(True, which="both", axis="x", linestyle=":", alpha=0.4)
plt.tight_layout()
plt.show()