Aggregation মানে অনেক rows থেকে summary value।

Data:

Restaurant   Sales
A            100
A            200
B            150
B            250

Total sales:

df.groupby("restaurant")["sales"].sum()

Output:

A → 300
B → 400

Multiple Aggregations

df.groupby("restaurant")["sales"].agg(
    ["sum", "mean", "count", "max"]
)

Aggregation প্রায় সব data analysis task-এর core।