Here is one option that I can think off..... So basically what you want is show the circle size based on the absolute value rather than the actual values (which could be negative or positive).
Just to demonstrate the example, here is what I have done -
1. Calculate the 2014 and 2015 Sales separately.
2. Calculate the Sales growth between 2014 and 2015 sales - Sales Growth.
3. Create a calc that captures the absolute value of Sales Growth. This will be added on the size pill.
4. With step 3 calc, size of the bubble will be range fro 0 through absolute value. Now to identify whether the bubble size is positive or negative, I created another variable - Sales Growth Indicator -
5. I drop Sales Growth Indicator on the color to explicitly show whether the growth is +ve or -ve.
Here is the final result - I hilighted 2 of the states to show how they look like - Hope you can simulate the solution in your case as well.
Sales change - example.twbx 1.2 MB
Thanks a lot for the thorough explanation. I realize that it might be the way forward, but I was hoping that there was a way to just tell the size indicator that I wanted to calculate the size as the absolute value - but I guess that isn't possible.
He is literally doing just that. Calculating the size as an absolute value and putting it on size.
Yes, that is quite obvious, thank you. But as I wrote in my original question, what I really was looking for was a way to do it without having to calculate anything. That is, just tell the size marks card, that i wanted the size to be centered around 0 - so I could avoid having to calculate a new absolute value variable. I want to avoid that, because the variable is chosen in a parameter, and it means I have to do an extra calculation for the tooltip for the parameter too.
I know I can do that (now), but if tableau had given me a way to do it inherently in the programme it would certainly be easier.
Well, to quote you
"..I wanted to calculate the size as the absolute value.."
You just want to be able to put it on a mark and right click and tick off a box like "Use absolute value" or something right? Personally I think that is a bad practice as it becomes less obvious what is happening in a viz if everything is hidden in formatting/manual settings on the marks. To each their own.