Pushing more calcs to Power Query - replacing DAX RANKX

Question

I have another Power Query calculated column challenge.
Customer introduced a new requirement. Staff can work multiple shifts in a single business date. They would like a flag if the timesheet entries overlap. Many of their establishments close after midnight, which makes calculations a bit trickier, but there
is a field for the "business date" of the shift which helps.
You can imagine source data like this:
Full Name Date Start Date End Date
Joe Smith 8/1/2014 8/1/2014 10:00 8/1/2014 18:00
Joe Smith 8/1/2014 8/1/2014 22:00 8/2/2014 1:00
Jane Doe 8/1/2014 8/1/2014 15:00 8/1/2014 18:00
Jane Doe 8/1/2014 8/1/2014 17:00 8/1/2014 17:45
John Brown 8/1/2014 8/1/2014 19:00 8/2/2014 1:00
John Brown 8/1/2014 8/1/2014 14:00 8/1/2014 16:00
John Brown 8/2/2014 8/2/2014 10:00 8/2/2014 18:00
Mary Black 8/1/2014 8/1/2014 18:00 8/2/2014 1:00
Mary Black 8/1/2014 8/1/2014 15:00 8/1/2014 21:00
Bob Walker 8/1/2014 8/1/2014 11:00 8/1/2014 14:00
Bob Walker 8/1/2014 8/1/2014 17:00 8/1/2014 22:00
Bob Walker 8/1/2014 8/1/2014 19:00 8/2/2014 1:00
In this case, Jane Doe, Mary Black, and Bob Walker have overlapping shifts. Joe Smith and John Brown do not.
I did the calculation in calculated columns in Power Pivot by ranking the start time on the date, ranking the end time on the date, then brute force checking to make sure the start and end dates are in the right order using some intermediate calc columns.
To do the ranking, I used the DAX RANKX function.
Now if I want to push this sort of logic back to Power Query. How do I do this? I do not see a ranking function in the formula reference as a starting point for my calculation. 
Thanks

Answer 1

Cathy, the following are a couple of rank functions I created as part of a custom stat function "library." Hopefully, they are self-explanatory.
//RankEqual Function
(inputValue as any, inputSeries as list, optional orderDescending as nullable logical) as number =>
let
    SortedSeries = if orderDescending or orderDescending = null then
                                List.Sort(inputSeries,Order.Descending)
                           else
                                List.Sort(inputSeries),
    RankEqual = List.PositionOf(SortedSeries,inputValue)+1
in
    RankEqual
//RankDense Function
(inputValue as any, inputSeries as list, optional orderDescending as nullable logical) as number =>
let
    SortedSeries = if orderDescending or orderDescending = null then
                                 List.Sort(inputSeries,Order.Descending)
                           else
                                 List.Sort(inputSeries),
    DistinctSeries = List.Distinct(SortedSeries),
    RankDense = List.PositionOf(DistinctSeries,inputValue)+1
in
    RankDense