count: Count rows by group
In basetable: Fast and Memory-Efficient Base R Table Manipulation

count

R Documentation

Count rows by group

Count rows in a table by one or more grouping columns.

count(data, by, sort = TRUE, name = "n", ...)

`data`	A data frame, or a single path to a delimited text file for the fused one-pass file mode.
`by`	Character vector of grouping columns.
`sort`	Whether to sort by descending counts. Ties (groups with the same count) are broken by ascending group key, so the row order is fully determined by `by` and `data` – never by the grouping engine's internal enumeration order, which is otherwise unspecified.
`name`	Name of the count column.
`...`	In file mode, reader options such as `where`, `delim`.