2  Keeping rows

keep takes a condition and keeps the rows where it holds.

R

sales |> keep(region == "West")

region	product	revenue	cost
West	Widget	100	40
West	Widget	200	50
West	Gadget	300	100
West	Gadget	150	50

Python

sales >> keep(col.region == "West")

region	product	revenue	cost
West	Widget	100	40
West	Widget	200	50
West	Gadget	300	100
West	Gadget	150	50

Conditions combine with and and or, and either language’s negation reverses one.

R

sales |> keep(revenue > 150 & cost < 100)

region	product	revenue	cost
West	Widget	200	50

Python

sales >> keep((col.revenue > 150) & (col.cost < 100))

region	product	revenue	cost
West	Widget	200	50

There is no separate verb for dropping rows. Removing the rows where something is true is keeping the rows where it is false, and one verb says both.

R

sales |> keep(!(product == "Widget"))

region	product	revenue	cost
West	Gadget	300	100
West	Gadget	150	50

Python

sales >> keep(~(col.product == "Widget"))

region	product	revenue	cost
West	Gadget	300	100
West	Gadget	150	50