So if you created a calculated field, something like this...
That should do the trick. Not that just through co-incidence the first week/day of 2017 fell on the 1st Jan. You can also adapt this "starting date" if your financial year doesn't start at the start of the calendar year. This is just the "base" date from which it works out how many weeks to add to this date for each Week/Year combination.
Let me know if that doesn't make sense, or doesn't solve your problem
thanks for the prompt reply on this issue. I tested the formula you provide me and it works fine, thanks! The only thing is, that the calculated date is always the last day of that specific week. How can i adjust this to gibe back the first day of that week? One more question: Is there any chance to get Tableau Prep adding data to a output file instead of creating always a new one? I have to collect data frequently once a week and it would be great if I just can use my Tableau prep workflow to only add the latest data in the file.
Sorry my bad...the formula should have been
Week 1 2017 would add one week to the #2017-01-01# I had used, not zero weeks!! So I've jogged the start back a week!
If your weeks started on a Monday, for example DATE(DATEADD('week',(([Year]-2017)*52)+[Week],#2016-12-26#)) would now start give the date for the Monday, so fiddling with this starting date should let you create the dates as you want.
With regards an incremental refresh, rather than a full refresh (as we can do in Tableau Desktop for tdes and hyper files). Unfortunately not yet (as far as I know). I imagine it will come in at some point (as Tableau Desktop can...and they seem to be gradually getting Prep upto the level of things we can do in Tableau Desktop).