Not OP, but here is an example using tidyverse (I leave the meaning of it to you; should be clear without any R knowledge): purchases |> group_by(country

Not OP, but here is an example using tidyverse (I leave the meaning of it to you; should be clear without any R knowledge): purchases |> group_by(country) |> filter(amount <= median(amount) * 10) |> summarize(total = sum(amount - discount))