By default, Tableau wraps both the prior and the current value in ZN, either or both of these could be removed by customizing the calculation. If a null value is returned as part of this expression the whole thing will evaluate as null.
I've demonstrated this in the attached workbook. Let me know if it helps.
Note I left the original difference calculation in my custom calculation so you can compare the difference between these. To get this I right clicked the table calc, selected edit table calc, then customize. If this isn't quite what you want then you may need to put back one of the zn() functions. ZN is short for zero null btw, meaning it will return a zero when the value inside the parenthesis is null.
hi Mr. Noah,
Thanks. I see it now.
Great! I'm glad I could help.
I tinkered around with the workbook a bit to show these different options, so you can see the impact of each choice a bit more clearly.
I tried using your calculation, but it doesn't really apply to what I'm trying to do (and was therefore useless to me).
The difference between my data and Phuviet's is that I have no calculations on mine. I just want it to be blank if there is no data. It's a straight data pull into a table.
Think you can help?