Help! My Shaded Density Plot Isn’t Curving

Hey everyone! I'm working on a programming assignment for a class, and I'm running into some trouble with my code. The task is to analyze two datasets – one with locations of 10,000 vaccinees and the other with 100 vaccination centers. I need to assign the vaccinees to the centers based on the shortest distance. After running my program on two different computers, I was supposed to compare the execution times and visualize the results with a shaded density plot.

I've run my code 50 times on both computers and collected the execution times, but when I try to generate the shaded density plot, it just shows a vertical line instead of a curve. My professor said it needed to be a curve plot to indicate the distribution difference. Here's the Python code I'm using:

```python
import pandas as pd
import numpy as np
import time
import seaborn as sns
import matplotlib.pyplot as plt
from scipy.stats import ttest_ind

# Load datasets
people_df = pd.read_csv("people.csv")
centre_df = pd.read_csv("centre.csv")
people_coords = people_df[['Lat', 'Lon']].values
centre_coords = centre_df[['Lat', 'Lon']].values

# Haversine formula
# ... (code continues)
```

I'm sure something in my code is causing the plot to not display correctly. Here are the specs for both computers I used:
**Computer 1:** MacBook Pro (2.2 GHz Quad-Core Intel Core i7, 16 GB RAM)
**Computer 2:** MacBook Air (Apple M1, 8 GB RAM)

I've shared some graphs that I generated but I can't quite understand why the shaded density plot isn't working as expected. If anyone can help me identify what's wrong with the code or how to fix my plot, I'd really appreciate it! Thanks!