Is the YEAR originated from a DATE field? If its a String, that might explain the error.
Post a packaged workbook example, and I'm happy to take a look--its difficult to guess at what's happening without seeing a workbook, or at least a screenshot showing your full screen, including all pills on all shelves.
No the years are numeric measures.
Again, post a packaged workbook and we can help you--otherwise, its nearly impossible to know whats going on. What field represents your Years? The screenshot helps, but not much, because we cannot view the data.
Allan is suggesting that you convert your integer year field into a true DATE field, using his formula, and use that in your view.
However, I'm not sure you've got the view set up properly for what you want to do, so posting a workbook would be ideal for all helpers.
Matthew, I'm trying to do the same thing as George T., and I also get the message, "Trend line cannot be computed error. Each axis should be number or date." I don't understand the message because the X-Axis is time in Months and the Y-Axis is sales revenue in Dollars. I could plot it on a graph myself and could calculate points along a linear trend line using Y=mX+b. Excel does a "graphical approximation" and displays the equation for the trend line and an "r-squared" value. I'm not understanding why Tableau can't
A colleague was trying to explain to me why - something about Tableau not interpreting the "Months" axis as a continuum but simply as column names. Do I need to format the cells as dates in Excel before I data into Tableau?
Thanks for any input that will help me do this. I'm sure someone has figured out a way to do it. Jack