To be well understood my question, what I do is a difference between a value belonging to 2015 and another that is a prediction, which belongs to 2016.
I apologize for the typos, because I am translating with google translator
Read this article by Brad
Breaking BI: Predictive Analytics in Tableau Part 1: Simple Linear Regression
Hope it helps.
Gallop Tab, Thank you for your help
The blog is very interesting, but it's not where my office is.
To make it more understandable, here I leave a picture, in which the objective is to determine the percentage difference between 2014 and 2015
Retrieving data ...