In this Tableau data visualization tutorial, we’ll learn to use the LOOKUP table calculation function to return sales revenue for the same day last year. A number of different techniques are used in the creation of this dashboard.

I designed this dashboard solely as a teaching exercise to help you understand the LOOKUP function and how to show the same date last year in a separate column.

• As we learned in a previous video Tableau Table Calculations Simplified, (make sure to watch this video afterwards for more clarity), we’ll compute using specific dimensions and then use “At the level” to make sure our LOOKUP table calculation is performing correctly.
• The “Show Missing Values” option is selected to fill in date gaps in the data set that do not exist. Ensuring 365 dates per year are present in the visualization enables the offset (i.e., -1) in the LOOKUP calculation to arrive at correct sales revenue from the same day in the previous year.
• You’ll learn that we can filter on a table calculation by using another table calculation. Filters based on table calculations do not filter out underlying data. Instead, the data is hidden from the view, allowing dimension members to be hidden from the view without impacting the data in the view.

Observe the Tableau filter order of operations above. Applying a dimension filter before the Table Calculation filter removes underlying data which affects the proper functioning of Table calculations. Typically, Table Calculations only work on values that are visible in the view. By applying a table calculation (which is last in the order of operations) you preserve underlying data but filter out data from the view.

Interact with this dashboard via the picture link:

You need to read these posts and watch these videos for additional information:

• Tableau Table Calculations Simplified
• Tableau Sales Dashboard Tutorial: Year Over Year Comparison

As always, If you find this type of instruction valuable make sure to subscribe to my Youtube channel.

All views and opinions are solely my own and do NOT necessarily reflect those of my employer.

In this Tableau data visualization tutorial I used a technique shared by Tableau Zen Master Ryan Sleeper to “equalize” dates across the same axis. This date equalization calculated field enables year over year, quarter over quarter, month over month, week over week and same day last year comparisons.

MAKEDATE(2018,MONTH([Your Date]), DAY([Your Date]))

Call in The Equalizer for this Analysis

It’s a pretty clever way of preserving the same month and day of date values across many years and updating their respective years to one common year.

For example, all dates would retain their current month and day but would share the year value of ‘2018’. In this manner, data points from various years can be stacked on top of each other for comparison purposes.

Additionally, by creating a parameter value for a specific date part (i.e., year, month, week, etc.,) the user has control over the level of comparisons in the visualization.

You’ll have to watch the video to see the details. Again, thanks to Ryan Sleeper for sharing this tip with the Tableau community which enabled me to apply it to my dataset and share it with you in video form.

As always, If you find this type of instruction valuable make sure to subscribe to my Youtube channel.

All views and opinions are solely my own and do NOT necessarily reflect those of my employer.