## LODs and Table Calcs - Data School Week 7

by Laura Peterson

#### Week 7 – LODs and Table Calcs -Let the Mind Melting Begin!

Week 7 was one of the toughest weeks yet; I was balancing being the team lead for the client project in afternoons with terrible morning training sessions from Head Coach Andy on LODs and Table Calculations in Tableau.

#### Table Calcs

Andy has written a fantastic blog on how to translate the table calc window into plain English that you can read here. It has helped me understand what is going on when I use Table Calculations.

There were a couple of ‘Ah ha!’ light bulb moments for me during the week. The first of which was that there are more table calculations available than the ones listed in the Quick Table Calculation drop-down

There’s more!

There are several additional table calculation functions, just to name a few:

• FIRST()
• LAST()
• LOOKUP()
• INDEX()
• SIZE()

Tableau help online has descriptions and examples of all these and more here.

The second big realisation was that you could add a secondary table calculation to particular types of quick table calculations:

This can come in very handy when making a Pareto chart for example, and you want to see the running total, but also know the percent of the total.

#### LODs

Level of detail calculations are slightly more difficult for me to understand than table calculations.  I started by going through the Tableau blog entry on the Top 15 LOD expressions.  There are four main LOD expressions:

1. { FIXED } – meaning for each field
2. { INCLUDE} – include a field that isn’t in the view
3. {EXCLUDE} – exclude a field currently in the view
4. { } – everything in the view

The Tableau blog does a great job of illustrating use cases for all for types of expressions. Most our exercises this week involved us creating two visualisations to answer the same question, using Table Calcs in one and LODs in the other.

#### More Mind Melting

On Wednesday Andy thought it would be fun for us to put our new found knowledge of reference lines and reference bands to work by tackling Workout Wednesday first thing Wednesday morning! He let us struggle along for just under an hour before moving back into our LOD practice. He even posted evidence of his cruelty on Twitter:

I got there eventually!

Laura Peterson

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