import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

rng = np.random.default_rng(9)
dates = pd.date_range("2020-01-01", periods=3 * 365, freq="D")
trend = 0.03 * np.arange(len(dates))
seasonal = 12 * np.sin(2 * np.pi * dates.dayofyear / 365)
noise = rng.normal(0, 2.5, size=len(dates))
series = pd.Series(80 + trend + seasonal + noise, index=dates)

monthly_mean = series.groupby(series.index.month).mean()
angles = np.linspace(0, 2 * np.pi, num=13)
values = np.concatenate([monthly_mean.values, monthly_mean.values[:1]])

fig = plt.figure(figsize=(6, 6))
ax = fig.add_subplot(111, projection="polar")
ax.plot(angles, values, color="#2563eb", linewidth=2)
ax.fill(angles, values, color="#93c5fd", alpha=0.4)
ax.set_xticks(np.linspace(0, 2 * np.pi, num=12, endpoint=False))
ax.set_xticklabels([f"{m}月" for m in range(1, 13)])
ax.set_title("月別平均値を極座標で表示")
ax.set_rlabel_position(90)
ax.grid(alpha=0.3)

fig.tight_layout()
fig.savefig("static/images/timeseries/seasonal_polar.svg")