ok, here’s another LOVE-HATE relationship topic for me (more on relationships in a future blog) but for now, I want to talk about LOD calcs.
These things are incredible. If you don’t know what they are, check out this blog and can see that with a simple calc, you can NOW do something that you are JUST not able to do without very complex formulas in other tools that are being called over and over again, making the whole system very fragile and brittle to changes.
LOD expressions completely changes that. You create a calculation where you can basically create and aggregate expression that is a different level than your viz. You want to see average YoY growth for your Sales at a Yearly Level, even when you data being shown at a Product Category Level. This sounds simple but it is a very complex problem for any BI tool and Tableau gave you a completely new way of doing things.
Having said that, just like I mention in my Table Calcs blog, you NEED to know what’s going on so you don’t end up creating a performance issue. Each LOD calc maybe dealt separately as a separate query to your data source and that could mean more load on your DB, more complex query structure to run the viz and that’s all I am going to say.
These are GREAT when used correctly but can create a devastating impact to your environment when NOT. I try to limit to 1 LOD calc per dashboard. It is a rule that I break more often than not in which case, my next limit to break might be 3 LOD calcs 😉