While revising for the Tableau Certified Data Analyst Exam, I thought it would be a good idea to do a series of Tableau Tutorials to consolidate my understanding for exploring and analysing data concepts. In this blog, I will be guiding you through what FIXED LODs (Level of Detail Expressions) are through a basic example, and a use case example from Bethany Lyons’ article: Top 15 LOD Expressions.
Fundamentals
FIXED LODs calculate aggregated values for stated dimensions independent of other dimensions in the view, and are expressed in braces. To demonstrate, let’s decipher the following syntax using the Sample – Superstore dataset.
As a reference, we will use the table below to show the value of the expression above.
We can clearly see there is no difference when dragging both measures [Profit] and [Profit per Category]. However, if we drag and drop another dimension (e.g. [Sub-Category]) onto the view, we will obtain a clearer understanding of what the FIXED LOD is illustrating.
In the table above, we can notice that the profits for each sub-category are different but the FIXED LOD expression states the same value for each sub-category. Hence, FIXED LODs are independent and do not refer to any other dimensions except for the specified dimension. Further, I added a totals row for each category for confirmation.
Use Case Example
This example will be covering the Customer Order Frequency from Bethany Lyon’s article using the Sample – Superstore dataset. Before diving into the calculations, let’s first take a look at the details by dragging and dropping [Customer Name] (preferably [Customer ID] if available) and a count distinct of [Order ID].
We want to provide a visualisation which returns the number of customers that have made 1, 2, 3, … , N orders as highlighted in the data labels above. To achieve this, we can use the following LOD.
This calculated field is a measure. To make this a label in our visualisation, we will convert it to a dimension. Drag and drop this dimension to the column shelf and an aggregated count distinct of [Customer Name] to the row shelf, and voila! We obtain a visual which illustrates the distribution of customer order frequency below.
We have now identified that 12 customers have made 1 purchase, 36 customers have made 2 purchases, etc.
If you have made it this far then I hope you have achieved a clearer understanding in FIXED LODs. Thank you for reading my first Tableau tutorial!