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.
grouped_df(data, vars, drop = TRUE)is.grouped_df(x)
is_grouped_df(x)
a tbl or data frame.
a character vector or a list of name()
if TRUE preserve all factor levels, even those without
data.