as_header: Create identifier columns in spreadsheet data
In MEDSL/medslcleaner: A MEDSL Package for Cleaning Election Returns

See the Excel vignette for use.

1 2	as_header(.data, idcol, rows = TRUE, cols = TRUE, right = FALSE, down = FALSE, .drop = TRUE)

`.data`	A table of tidy spreadsheet data (i.e., with columns `row`, `col`, and `value`).
`idcol`	String giving the name of the new identifier column.
`rows`	One of: a vector of spreadsheet row indexes; a logical vector with length equal to the row count of dataframe `.data`; or a length-one logical vector (i.e., `TRUE` or `FALSE`) applied to all spreadsheet rows.
`cols`	One of: a vector of spreadsheet column indexes; a logical vector with length equal to the column count of dataframe `.data`; or a length-one logical vector (i.e., `TRUE` or `FALSE`) applied to all spreadsheet columns
`right`	If `TRUE`, carry non-missing values in cells selected by `rows` and cols`rightward along spreadsheet rows. Can be used together with`down'.
`down`	If `TRUE`, carry non-missing values in cells selected by `rows` and cols`downward along spreadsheet rows. Can be used together with`up'.
`.drop`	If `TRUE`, drop spreadsheet cells selected by `rows` and `cols` after creating the new identifier column.