Box Plot Custom Whisker Value
Jennifer VonHagel Dec 5, 2018 12:08 PMHello community,
I have very specific requirements for a box plot chart. I will have multiple box plots shown by dimension, and each set of marks and corresponding box plot need to be assigned specific colors. The formatting and end result prettiness of this chart is really important. There will always be multiple dimension values shown in the same view  probably at least 15.
Using the principles of Yuri Fal's response in this thread Educational Brain Teaser: Coloring the Boxes on Box and Whisker Plots , I've gotten to a place of being able to assign colors to each dimension in the sample dataset attached.
However, I need the whiskers of the box plot to be within 0.5 of the IQR, not within 1.5 of the IQR (see screenshot box plot options below).
I can easily calculate all the various components of the box plot, including my custom whisker values...
Median: percentile(value_at_some_fixed_level,.5)
1st Quartile (start of box): percentile(value_at_some_fixed_level,.25)
3rd quartile (end of box): percentile(value_at_some_fixed_level,.75)
IQR (interquartile range: 3rd quartile  1st quartile)
Lower Whisker (1st Quartile  0.5*IQR)
Upper Whisker (3rd Quartile + 0.5*IQR)
...and then add reference lines and distribution bands to simulate whiskers and the box, but the formatting looks terrible. The reference lines and bands necessarily span the entire height of each subcategory's row, and there is no good way to get the difference colors per subcategory. The whisker height in the scenario would also be the entire height of each row, which again just doesn't look nice. With this option there isn't a really good way to get the black lines that extend from the box to the whiskers (I could maybe do a gantt style chart on a dual axis, but then I have no chance at all to create the different box colors based on a gantt dual axis).
I've looked at Tableau extensions to see if there were any further box plot options, and didn't find anything.
I've heard Tableau is essentially an XML file. Is there any way for me to hack into the backend and just change the 1.5 of IQR to 0.5? Or any other ideas?
Thanks,
Jennifer

Box Plot Custom.twbx 348.9 KB