GroupBy—Transform and Filter

Overview of transform

Having seen how to aggregate grouped data, we'll now switch gears and learn how to apply transform functions. In general, the transform operation applies a function to each group, and the resulting scalar value is then assigned to each row of every group.

When used on grouped data, transform functions perform group-wise computations and return an output indexed the same way as the original DataFrame. Let’s use the credit card dataset to illustrate how this works on grouped data.