This is the front-end solution:
Let me know if you need the back-end solution as well.
Hope this helps.
Peek for charts.qvw 147.2 K
Back end solution could be like this:
LOAD Date(Date#(EventDate, 'MM/DD/YY')) as EventDate,
LOAD * Inline [
If(Peek('Location') = Location, RangeSum(EventDate - Peek('EventDate'))) as DaysSince
Order By Location, EventDate;
DROP Table Table;
Community_181894.qvw 147.2 K
I like both of these options but I have realized one small issue. If I want to just compare the EventDate to the previous one without regards for Location then these solutions wont work. This isnt a huge deal as I believe I could create a graph with each expression representing a different location.
I guess you can create a separate DaysSince for just Date or you can make Sinan's front end solution to be dynamic so that you can compare it with regards to location or by disregarding location with a button click.
Ultimately it all depends on what your requirement is.