tibble_combn: Apply a function across all combinations of groups in a...
In fennerm/fen.R.util: Fenner's personal R libraries

All extra parameters are passed to the input function

1	tibble_combn(tbl, set_size, func, within = NULL, ...)

`tbl`	A nested tibble
`set_size`	Number of rows in dat to compare in each iteration
`func`	function Function to apply to each set of rows
`within`	character A column name from the inner nested tibbles in 'tbl'. If given, comparisons will only be made between rows which share the same group in the within column.