Thanksgiving Day NFL Games

Sean Miller posted this week’s challenge based on the results of the annual NFL games hosted on Thanksgiving Day. It immediately reminded me of a previous #WOW challenge that Lorna posted in 2019 when she visualised Rugby League wins (see my viz here).

This is a table calculations based challenge. I did start using FIXED LoDs to help calculate the summary measures (Total Games and Win %) displayed at the front, but found that as there are 2 years (1975 and 1977) when the Dallas Cowboys did not host a game, I ended up with some pesky NULL values displaying which affected how the running sum area chart displayed.

Defining the calculations

As its a table calc challenge, I’ll build out what I can into a table to start with, to sense check I’m getting the correct numbers.

First up add Home Team, Game Date and Visiting Team to Rows and display Home Score and Visiting Score.

We start by determining the result of the fixture, based on whether it’s a home or away win or a tie. In the lollipop chart home wins are plotted at 1 and away wins at -1, so we’re going to store the result as a numeric value rather than text.

Result

FLOAT(IF [Home Score]>[Visiting Score] THEN 1
ELSEIF [Home Score]<[Visiting Score] THEN -1
ELSE 0 END)

The output is wrapped within a FLOAT, as this will help how the axis displays. Without it, by default Tableau will define the field to be a whole number, and the axis will extend to +/-2 which is too much room. We can’t adjust (fix) the axis to a decimal if the field itself is an integer, and adjusting to +/-1 chops off the displayed marks.

If you add this to the display, it will show 1, 0 -1 as you expect. You’ll notice though that the Axis on the lollipop chart is labelled as Win/Loss. This is achieved by applying a custom format to the field – “Win”;”Loss”;”Tie”

This is a sneaky but effective trick. The information stated before the first semi-colon applies to positive numbers, the info after the first semi-colon applied to negative numbers, and the information after the optional second semi-colon applies to zero.

Unfortunately though, it would appear that, at the point of writing, Tableau Public, isn’t honoring the zero formatting, and is displaying Win rather than Tie. The display works on Desktop though.

The win/loss/tie text is just a formatting feature and affects what is displayed, but the underlying value is still a number.

The Result field will be used to plot the lollipop chart. We now want a field to plot the area chart against. This is a running total of the Result values (ie win =1, win, win = 1+1, win, win, loss = 1+1 -1) and we need a table calculation.

However, as stated above due to a couple of missing years, I had to make an adjustment to ensure the running total displayed as Sean had in his challenge. I created another field

Result Adjusted

IIFNULL(SUM([Result]),0)

If the Result field doesn’t exist, as there is no data, then use 0 instead.

To see what’s going on, we’re going to need a different view of the data where the date field is continuous (green) rather than discrete (blue).

Build the below, and filter just for the first 10 years – you’ll see the gaps where the are no marks in 1975 and 1977 for Dallas

Use the context menu of the green YEAR(Game Date) pill and select the option to Show Missing Values. Marks will now display

Add Result to Label. Each mark is labelled Win or Loss, except the ones for Dallas for 1975 & 1977 as there is no data

Now add Result Adjusted to Label. A 0 value is now displayed against those two marks.

We can now build a running total off of this measure instead

Running Total Wins

RUNNING_SUM(([Result Adjusted]))

Add this to the Label too and verify the table calculation is computing by the Game Date field only. The running total for the 2 ‘missing’ dates is displaying a value which is the same as the previous value (since we’ve added 0 onto the running total). This will give us the flat line in the area chart when we come to build it.

Now back to our table of data, we can focus on the other calculated fields we need….

Total Games

WINDOW_COUNT(COUNTD([Game Date]))

This is a table calculation and is simply counting the number of distinct dates displayed. Add this to the table display we were building to start with, and adjust the table calculation to compute by all fields except Home Team. The total should display the same value for all the rows against each Home Team.

Next we want a field to indicate if the row is a win.

Is Win?

INT([Home Score]>[Visiting Score])

This is taking a boolean of true or false and converting to an INT (1 or 0).

From this we can work out the Win rate

Win %

WINDOW_SUM(SUM([Is Win?]))/[Total Games]

Add up all the Is Win? values associated to the Home Team as a proportion of the Total Games played. Format this field to a percentage with 0 dp. Again, add to the table and adjust the table calc to compute by all fields except Home Team, and verify the same settings applied to both the calculations nested in this calculation

For the All-Time Record, we need to know the number of wins and number of losses. We have a field to help us with the wins, but need an equivalent for the losses

Is Loss?

INT([Home Score]<[Visiting Score])

And from this we can work out

All-Time Record

STR({FIXED [Home Team]: SUM([Is Win?])}) + ‘-‘ +
STR({FIXED [Home Team]: SUM([Is Loss?])})

This is the one field I kept from my LoD based attempt.

The circles on the lollipop chart are coloured based on the difference in the score, so lets’s create that

Score Difference

[Home Score]-[Visiting Score]

And finally we need some fields to help display the tooltips properly. The tooltip indicates whether the result was ‘won’ or ‘lost’ which is different text to the axis labels.

TOOLTIP-Result

IF [Result]=1 THEN ‘won’
ELSEIF [Result]=-1 THEN ‘lost’
ELSE ‘tied’
END

The tooltip also displays the scores, but the scores are always presented as highest score – lowest score and not home score – visiting score. So we need fields to store the right values

TOOLTIPHigher Score

IF [Is Win?]=1 THEN [Home Score] ELSE [Visiting Score] END

TOOLTIP – Lower Score

IF [Is Loss?]=1 THEN [Home Score] ELSE [Visiting Score] END

Pop all these fields out onto the table, so you can validate you’ve got all your calcs right before building the viz.

Building the area chart

Add Home Team to Rows, Game Date (continuous, show missing values) to Columns and Running Total Wins to Rows (ensure table calculation set as required). Change to mark type of Area. You should have 2 horizontal lines from 1974-1975 and 1976-1977 against the Dallas Cowboys row.

Adjust the tooltip, edit the label of the Running Total Wins axis , and remove the label of the Game Date axis.

Building the lollipop chart

Now add Result to Rows directly after the Home Team pill. Change the mark type to circle.

Add Score Difference to the Colour shelf of the circle mark, and adjust the starting colour range to a dark grey. Readjust the colour of the area chart to blue too. Add a border to the area chart too (via the colour shelf).

Add another instance of Result to the Rows shelf, next to the existing one. Set the mark type of this to bar. Reduce the size to the smallest possible, set the colour to grey and remove the border.

Now set this to be dual axis, synchronise the axis, and set the marks of the 2nd Result axis displayed on the right hand side to move marks to back. Uncheck Show Header to remove this axis from displaying.

Add Visiting Team, TOOLTIP-Result, TOOLTIP-Higher Score and TOOLTIP-Lower Score to the Tooltip shelf of both the Result marks cards, and adjust the tooltip on both to

Remove the Column dividers.

Now drag Total Games to Rows and drop next to the Home Team field. Change to be discrete (blue). Verify the number is what you expect and adjust the table calc if need be.

Add All-Time Record and Win % (set to discrete) to the view too. Then format these 4 fields so the text is larger and aligned centrally.

All that’s left now is to add the sheet to a dashboard. My published viz is here.

Happy vizzin’! Stay Safe!

Donna

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