Exercise Heart Rate Distribution

import matplotlib.pyplot as plt
import numpy as np
from scipy import stats

np.random.seed(202)

hr = np.concatenate([
    np.random.normal(100, 15, 300),
    np.random.normal(140, 20, 400),
    np.random.normal(170, 15, 200)
])
hr = hr[(hr > 60) & (hr < 200)]

kde = stats.gaussian_kde(hr)
x = np.linspace(60, 200, 500)
y = kde(x)

colors = ['#1e3a8a', '#3b82f6', '#22d3ee', '#fbbf24', '#f97316', '#dc2626']

fig, ax = plt.subplots(figsize=(12, 6), facecolor='#ffffff')
ax.set_facecolor('#ffffff')

for i in range(len(x)-1):
    norm_val = (x[i] - 60) / 140
    color_idx = int(norm_val * (len(colors) - 1))
    color_idx = max(0, min(color_idx, len(colors)-1))
    ax.fill_between(x[i:i+2], y[i:i+2], alpha=0.6, color=colors[color_idx])

ax.plot(x, y, color='#374151', linewidth=2.5)

zones = [(100, 'Warm-up'), (130, 'Fat Burn'), (155, 'Cardio'), (175, 'Peak')]
for val, label in zones:
    ax.axvline(val, color='#9ca3af', linestyle='--', linewidth=1.5, alpha=0.7)
    ax.text(val+2, max(y)*0.85, label, color='#6b7280', fontsize=8, rotation=90, va='top')

ax.set_xlabel('Heart Rate (BPM)', fontsize=12, color='#1f2937', fontweight='500')
ax.set_ylabel('Density', fontsize=12, color='#1f2937', fontweight='500')
ax.set_title('Exercise Heart Rate Distribution', fontsize=16, color='#1f2937', fontweight='bold', pad=15)

ax.tick_params(colors='#374151', labelsize=10)
for spine in ax.spines.values():
    spine.set_color('#d1d5db')
ax.grid(True, alpha=0.3, color='#e5e7eb')
ax.set_xlim(60, 200)

plt.tight_layout()
plt.show()