This collection of functions accesses data about grouped data frames in various ways:
group_data() returns a data frame that defines the grouping structure. The columns give the values of the grouping variables. The last column, always called .rows, is a list of integer vectors that gives the location of the rows in each group.
group_keys() returns a data frame describing the groups.
group_rows() returns a list of integer vectors giving the rows that each group contains.
group_indices() returns an integer vector the same length as .data
that gives the group that each row belongs to.
group_vars() gives names of grouping variables as character vector.
groups() gives the names of the grouping variables as a list of symbols.
group_size() gives the size of each group.
n_groups() gives the total number of groups.
See context for equivalent functions that return values for the current