For #WOW2020 Week 48, Jami Delagrange set the challenge based on a problem she’d been puzzling over for a while.

The data set was one Jami created herself about turkeys creating a ‘conference’ (it is Thanksgiving week in the US).

The above is basically 2 bar charts plotting the time an event happened (on the x-axis) against the number of turkeys attending the event (on the y-axis). One bar chart is coloured based on the location, the other is a white bar which has a width based on the duration of the event.

There are a couple of calcs needed for the basic data

# Turkeys

COUNTD([User Name (Original Name)])

Duration (mins)

DATEDIFF(‘minute’,[Start time],[End time])

With these we can get a basic set of data

The Start Time and End Time fields can be custom formatted to hh:mm AMPM.

The first bar chart we need is very simple, plotting Start Time against # Turkeys, coloured by Location.

For the second chart, we need to make use of the Size shelf, and the feature that allows you to fix the size based on a field. If we add Duration (mins), we don’t get what we need

The bars are far too wide. As the Start Time being plotted is at the ‘minute’ level, each unit of the axis is 1 minute of a day. There are 24 * 60 = 1440 minutes in a day. So the size needs to be based as a proportion of the number of minutes in a day ie

Duration Proportion of Day

[Duration (mins)] / (24 * 60)

Adding into our data table, you can see what these values translate to

and if we drop this onto the Size shelf instead, we get the required display

Build these charts as a dual axis, and you’ve got the output. Tableau’s own help article, discusses the Size feature a bit more.

My published viz is here.

Happy vizzin’! Stay Safe!

Donna