The easiest way to create a grouped data frame is to call the group_by()
method on a data frame or tbl: this will take care of capturing
the unevaluated expressions for you.
These functions are designed for programmatic use. For data analysis
purposes see group_data() for the accessor functions that retrieve
various metadata from a grouped data frames.
Usage
grouped_df(data, vars, drop = group_by_drop_default(data))
is.grouped_df(x)
is_grouped_df(x)