Originally published in March 2023 for International Women's Day, #DiversityinData's Women's History Month, and #SWDchallenge for remaking a famous graph, this viz is a tribute to one of the women who has made a significant impact in data visualisation, Florence Nightingale. This is also an apt post for this month's theme on the blog, History of Data Visualization: Pie Chart. Click on the image above to go to the Tableau Public page for this viz. Although the rose diagram is not strictly a pie chart, it can be considered a variation. Unlike a pie chart, the rose diagram aka coxcomb or polar chart does not have wedges that change proportionately to the total value. The wedges are pushed outwards as the values increase instead, and vice versa.
This data viz deserves a post on its own not only because of this month's theme but also because of my desire to share how I have created this viz on Tableau. Tableau does not allow users to organically create rose diagrams. I have to figure out my own way to recreate the viz at the point of the creation of the viz. I will admit the rose diagrams are not exactly accurate due to the following. I have reimagined the charts in Tableau using shapes and floating tiles. Unless Nightingale's charts are not proportionate in the first place, mine is not accurate by all means as seen by overlaying my charts over the original viz (see below). With my viz being a tribute and not for business needs, it may be acceptable at some level.
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As you may already know, shapes in Tableau can be "hacked" by using a transparent background and centering the object in the image from my blog post a while back. I have done the same for this viz. Nonetheless, I am prepared to do a tutorial on how to do this in next week's post. Hence, this post will focus on the mentality and idea behind recreating the viz on Tableau rather than a step-by-step guide on how to create wedges and put them into Tableau to generate a rose diagram. With that said, here is my sharing in ABC:
Advancement
Compared to the times of Nightingale, I am supposed to have an easier time creating the rose diagram. However, this is not the case. Using Tableau as the primary tool for this viz, I am hindered by creating Tableau limitations in creating out-of-the-box charts. I have to work around the issue. Using the Marks card where I can input the shapes and sizes. I have sized up the shapes using Tableau's Synchronise Axis. Perhaps, I shall try creating charts without a computer as a challenge next time. It may also be for the better for Tableau to keep its chart types to ones that promote graphical integrity.
Betterment
On the other hand, I have used Tableau to add 3 quality of life elements to the viz.
1. An interactive layer to highlight either of the 3 categories. With some of the wedges being too small or covered up by other wedges (Tableau issue), the additional layer helps users refer to specific wedges better. Recalling that Nightingale presented the viz to the royals, this may have helped her or users today.
2. Admittedly, the tooltip is meant to overcome the problem of highlighting specific wedges in Tableau as shapes overlap with each other. However, this improves the user experience as users can immediately know the numbers for each wedge. Considering the wedges have no axes to refer to and labels, the tooltip solves the problem of this viz being just a beautiful visual without acknowledging the actual numbers.
3. The font used for the chart may have been in trend during the first printing of the book, but it is difficult to read to me. I have a hard time deciphering the words while trying to copy the text, and it is frustrating even with the high resolution of the image. As such, I have updated the font to the commonly used Arial. The coloured fonts also act as legends.
Correctness
Seeing how my viz does not exactly fit Nightingale's original one when I put one on top using the transparent background to compare both rose diagrams. I do have doubts that I have managed to visualise the data correctly with Tableau. Perhaps, proportionately the graph is not far off as the Size marks card does take into account the smallest and largest value when sizing. Additionally, as a tribute and visual art piece, this works.
All in all, it has been fun exploring not only shapes on Tableau but also a famous viz from the past. There are definitely quite a number of write-ups online but I have found this particular podcast by Tim Harford interesting. It argued that although Nightingale could have used a simpler chart, the rose diagram as part of the presentation managed to sell a story better with the numbers.