As you may have noticed, three of the companies (AAPL, IBM, and MSFT) are tech companies, while the remaining three companies are not. Stock analysts often group companies by industry to gain deeper insights. Let's try to label the companies by industry:

# Classify companies by industry
tech_companies = set(["AAPL","IBM","MSFT"])
stock_df['Industry'] = ["Tech" if c in tech_companies else "Others" for c in stock_df['Company']]