If you're just using a table, then you can use this formula
[PreviousValue] : lookup([KPI1],-1)
to fetch the previous value for the month for each vendor. In this picture I am using Table (Down), but you may need to change this to Pane (Down)
You can then use this formula to make a shape.
[KPI1 Shape]: iif(ZN([KPI1]) - LOOKUP(ZN([KPI1]), -1)<0,"down","up")
Try it out
I'm sorry but I'm really newbie on Tableau.
I was trying to create the calculated field but I'm not able (it is throwing me an error in the lookup)
Is there any way you can put what you've explained me in a tableau example file?
Thanks in advance,
First, sorry for the delay in my answer. It was a bit difficult to find a computer to install Tableau 9
Second, I was able to resolve my issue of the lookup by using this KB"Error “All fields must be aggregate or constant…” | Tableau Software"
Third, I would like to thank you because your proposed solution worked like a charm! Thank you very much for your help!!!