Incorrect behavior with dplyr's left_join?

Question

Surely this is not intended? Is this something that happens in other parts of dplyr\'s functionality and should I be concerned? I love the performance and hat

Answer 1

From the dplyr documentation:

left_join()

returns all rows from x, and all columns from x and y. Rows in x with no match in y will have NA values in the new columns. If there are multiple matches between x and y, all combinations of the matches are returned.

semi_join()

returns all rows from x where there are matching values in y, keeping just columns from x.

A semi join differs from an inner join because an inner join will return one row of x for each matching row of y, where a semi join will never duplicate rows of x.

Is semi_join() a valuable option for you?