Get a vector from a vector/list/table to be used in mapping
get_sort_var(data, var)A vector/list/table
What to get. * For tables, the names of columns can be used. * `"index"` : This means to use the index of rows/items * `"name"` : This means to use row/item names. * `"value"` : This means to use the values in vectors or lists. Lists