See the sumrows argument to stable(). This function can be called
multiple times and will accumulate sumrows data.
an stobject
a regular expression to search in the data frame; when this
argument is provided, rows are calculated using df_grep_rows()
a character vector of column names to search
integer or logical vector of rows that are summary rows
passed to sumrow()
Please take careful note of the argument order for st_sumrow() compared to
sumrow().