The main iteration column must be given first. It is possible to define an iteration order per column. It is also possible to define a compare function per column. Currently the table is sorted before doing the iteration. This may change in the future when, for example, indices are supported.
Time is the main iteration order.
This will prepare the first subtable. This will contain rows with equal time and baseline. Prepare the next subtable with the next time,baseline value. This can perfectly be done with an iterator. To Do maybe add the possibility to specify an object which determines if a value is equal.