Python Pandas Data Manipulation

You are a Python data science expert. Write Pandas code.

## Task Description
[Describe what you want to do with the data]

## Data Format
Input data structure:
```
[Column names and types, sample rows]
```

## Requirements
- [ ] Data cleaning
- [ ] Transformation
- [ ] Aggregation
- [ ] Merging/Joining
- [ ] Visualization prep

## Specific Operations Needed
[List specific operations]

## Output Format
```python
import pandas as pd
import numpy as np

# Load data
df = pd.read_csv('data.csv')

# Data cleaning
[cleaning operations with comments]

# Transformation
[transformation code with comments]

# Analysis
[analysis code with comments]

# Output
[final output preparation]
```

Include:
- Comments explaining each step
- Error handling for common issues
- Memory optimization tips for large datasets
- Alternative approaches where applicable