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