Can you create a common starting point?

Kyle set the challenge this week, revisiting his favourite topic – baseball. The aim was to build what I’ve often referred to as a ‘rocket chart’, as it charts progress from a single ‘launch’ date/point. However having had a quick google, I can’t see any other reference to this being used for this type of chart….no idea where it came from <shrug>.

Anyway, the requirement was to compare the profiles of when home runs (HRs) had been accumulated over the course of a player’s career, restricting to just the players who are in the all-time top 10. These players hadn’t necessarily played during the same years or even decades, so there was a need to baseline the information according to the days since they started. Kyle also threw in the requirement that this was to be an LoD based challenge only, with no use of table calculations.

Build the basic chart

As mentioned above, we first need to ascertain how many days have passed between when the player hit their first home run, and the subsequent dates. We use a FIXED LoD to work out the minimum date per player

Min Date Per Player

DATE({FIXED [Player] : MIN([Date])})

And with that we can the work out the number of days that have passed

Days Since Min Date

DATEDIFF(‘day’,[Min Date Per Player], [Date])

And with this, we can quickly build out the main crux of the chart. Add Days Since in Date to Columns, and change to be a continuous dimension. Add Career HR to Rows and amend the aggregation to use AVG rather than SUM, as I found there looked to be duplicate records for some dates for the same player. Add Player to Detail.

Colouring the lines

Kyle provided a custom colour palette to use based on the team colours of the player. I updated by preferences.tps file with this data, and closed and reopened Tableau Desktop to ensure it picked it up. For more information on working with custom colour palettes see this Tableau help article.

Along with the player colours, we also need to identify which player has been selected.

For that we need a parameter to define who the selected player is


string parameter using a List where the values are added from the Player dimension. this causes the default to be set to Albert Pujols.

Show the parameter on the display.

We can now create

Is Selected Player?

[Player] = [pPlayer]

which will return a boolen true/false.

Kyle stated that we should be able to set the colours without having to manually click against every Player|T or F combination.

Now I managed this when I first built my solution, but in writing this blog and trying to replicate the steps, I’m not getting the same behaviour. So I have managed to come up with another way. The gif below hopefully demonstrates, but I’ll list the steps too.

Move the Player pill from Detail onto Colour

Edit the Is Selected Player field to just return True (use // to just comment out the original calculation)

Add Is Selected Player to the Detail shelf, then click the detail icon to the left of the pill and change it to Colour. This is a way to get multiple pills on the Colour shelf. Dragging will just replace the field being used for colour.

The colour legend dialog box should display a list of <Player>, True entries (if the legend isn’t displaying go to Worksheet > Show Cards > Reset Cards – you may then have to add the parameter to the display again).

Edit the colour legend, select the MLB HR Top 10 colour palette and click Assign Palette. This will automatically assign the relevant colour to each entry, since they were added based on alphabetical order.

Re-edit the Is Selected Player field, so it is back to [Player] = [pPlayer].

The entries in the colour legend will now only list one <Player>, True entry and the rest all false.

Edit the colour legend, and multi-select (ctrl-click) all the False entries, and then select the lightest shade of grey from the Seattle Grays palette. This should give you the desired display.

Select Alan Rodriguez from the parameter control. Both Albert, False & Alan, True should now be coloured. Edit the colour legend again and manually set the Albert Pujols, False entry to the same grey shade.

Now if you select any other player, only 1 line should be coloured, and it should be coloured to the corresponding player’s colour.

Setting the Tooltip

Add Season HR to Tooltip and change the aggregation to AVG. Add Date to Tooltip too and set it to be an Attribute. Amend the tooltip accordingly.

Adding the highest season HR indicator

Firstly we need to determine what the maximum Season HR value is per player

Max Season HR Per Player

{FIXED [Player]: MAX([Season HR])}

With this, we then want to get the corresponding Career HR value for that same time.

Career HR | Max Season HR

IF [Season HR] = [Max Season HR Per Player] THEN [Career HR] END

Add this field to Rows and change the aggregation to Avg.

Set to Dual Axis, Synchronise Axis and then set the mark type to Circle. Adjust the size of the circle mark slightly if need be.

Labelling the lines

On the Line marks card, add Player and Career HR to the Label shelf. Adjust the aggregation of Career HR to Avg. Edit the label, so only line ends are labelled. Adjust the font size to something quite small, and set the colour to Match Mark Colour.

Finally remove all gridlines, row & column dividers, and hide the axis. Title the chart.

When added to a dashboard, I then used a floating text object for the introductory text and positioned the parameter as a floating object underneath the text.

My published viz is here.

Happy vizzin’!



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