First, thank you for this resource. I have learned so many things just from searching the forums. I have a question that keeps coming up with my data that I have so far been unable to solve by myself. I am hoping someone can help me with this calculated field so I can better understand how tableau works.
The question I am trying to answer is "How has the client's share changed (absolute difference) year over year from the pre period to the post period (a before and after a change at the client)?" I can easily calculate the answer by week, month, quarter, etc. - anything involving the calendar date dimension. However, when I want to aggregate at the "pre period" vs. "post period", my calculations break since I have removed the date from the view. I just can't for the life of me figure out how to get the right answer. I want to show the pre and post periods aggregated. Please see sheet 4.
While working on a new data set yesterday, I noticed a strange new problem (sheet 3). If my first year of data (2011) is incomplete - it starts in week 37 to the end of the year (16 weeks of data) - then the year over year growth calculation does not work as expected. I would expect that it begin to show the YOY change at week 37 of 2012 year and going forward. Instead, it compares the first 16 weeks of the 2012 year to the last 16 weeks of 2011, then has a big gap of no calculations for the rest of 2012, then works as expected (I think) in 2013.
Thank you in advance for your help. I have attached a workbook to illustrate.