row_group_meta() and column_group_meta() returns the grouping structure,
in a data frame format. See dplyr's dplyr::group_data(), from which the
functions are based. Returns NULL for ungrouped matrixsets.
row_group_keys() and column_group_keys() retrieve the grouping data,
while the locations (row or column indices) are retrieved with
row_group_where() and column_group_where().
row_group_indices() and column_group_indices() each return an integer
vector the same length as the number of rows or columns of .ms, and
gives the group that each row or column belongs to.
row_group_vars() and column_group_vars() give names of grouping
variables as character vector; row_groups() and column_groups() give
the names as a list of symbols.
row_group_meta(.ms)row_group_vars(.ms)
row_group_keys(.ms)
row_group_where(.ms)
row_group_indices(.ms)
row_groups(.ms)
column_group_meta(.ms)
column_group_vars(.ms)
column_group_keys(.ms)
column_group_where(.ms)
column_group_indices(.ms)
column_groups(.ms)
a matrixset object