Florence Nightingale's Famous Rose Chart (aka ＂Coxcomb＂)

This is Florence Nightingale's famous Rose Chart. It shows how the changes she made at a British Army field hospital in the 1850s dramatically reduced the number of people dying from disease. This chart helped her establish the modern field of nursing. As peculiar as the chart is, it fulfilled its intended purpose. But how did it actually work? What data was it based on? And why did Nightingale draw such an unusual chart? Let's take a look. To understand this chart, we have to look not just at the chart itself and what it depicts, but also the purpose for which it was made and the person who made it. And I also want to clear up some of the misconceptions around this famous chart. What it shows is the number of people dying at a field hospital in a place called Skotari during the Crimean War in the 1850s. This war was fought between Russia on one side and a coalition of France, the Ottoman Empire, the United Kingdom, and Sardinia on the other. Skotari is known as Üsküdar today and is now part of Istanbul. Back then, it was a separate town across the Bosporus from Constantinople. There are actually photos of the British camp at Skotari, which is pretty impressive since this was still very early days for photography. You can actually see the hospital in the back there. It's a massive building and still stands today. Florence Nightingale was there to improve the conditions under which the British soldiers were being treated, and she did something that was still pretty new at the time. She collected data about the causes of death at this hospital. She wanted to be able to show that the changes she made had an effect. The chart is kind of peculiar. It consists of two parts and they are read from right to left. The two circular charts or diagrams consist of segments that each represent one month, starting on the right chart with April 1854 in the nine o'clock position and going around clockwise to March 1855. The different colors of the wedges show the different causes of death. Red means death from wounds sustained in battle, blue from disease, and black are all other causes. So the right-hand chart shows one year of data, April 1854 to March 1855, and then there's a jump over to the left where we see another 12 months of data, April 1855 to March 1856. This chart works the same way, with blue being the number of deaths from disease again and the direction of the chart going around clockwise. These two separate diagrams show before and after of the sanitary changes that were made to the hospital, and Nightingale's point was to show that far fewer men were dying from infectious diseases, shown in blue, once those changes had been made. And that is pretty obvious here, I think. I've also seen people question if the encoding had been done correctly, because if you were to size the wedges by scaling their radius linearly, you would get an exaggerated effect, since the area of the wedge increases with the square of the radius. But Nightingale explains in the caption very clearly that this was done by area, so this was done correctly. It was not Nightingale's intent that this chart would be used for any sort of analysis. In contrast to Charlotte Minard, we know a lot about Nightingale. She published a number of books and pamphlets, and she wrote many letters that still exist in archives today. This chart was first published in a report that had tables with the numbers that it was based on. So if you wanted to get the exact values, you'd look at the table. What were you doing trying to decode them from this chart? I've been wondering why it was drawn right to left, and why it started in the nine o'clock position in each of the circular diagrams. R.J. Andrews, who has done a lot of research on historical data viz, thinks that it's because in a circular chart, you would expect summer to be at the top and winter at the bottom. If you also expect the chart to read clockwise, that pretty much tells you where the other months have to go. And since her data starts in March, that dictates where the chart has to begin. The right to left transition, then, is a consequence of the first circle being much larger due to the numbers being larger. So if you want to indicate the connection with a line, so that you see that chump, you need to go right to left. That's really your only option. This chart was meant for a particular audience, what Nightingale liked to call the vulgar public. And that didn't mean the general public, which wasn't going to understand this chart anyway, but members of Parliament, the Secretary of War, and Queen Victoria and Prince Albert. These were the people whose support you needed to make the changes happen to the way people were being treated at those hospitals. Florence Nightingale isn't just known for this chart, she's known for having established the modern field of nursing. Let that sink in for a moment. She literally founded nursing. She wrote the foundational text of the field in 1859, and it's still in print today. And she used data and charts and the still fairly novel field of statistics to convince the powers that be that it made sense to not just let their soldiers die from horrible and preventable diseases, but to care for them and bring them back. Before Nightingale, nursing was not a respectable profession and was not based on any kind of scientific or systematic approach. Medicine back then was also horrifically uninformed. You have to realize that this was before even the germ theory of disease. A common idea at the time was that disease came from the miasma, the general foul smell you'd find in overcrowded and poor parts of cities at that time or around army field camps, and they just really couldn't do much about it. The field hospital in Skotari was in horrendous shape. I couldn't find any photos from the actual hospital, and I doubt that they were able to take pictures inside in the 1850s, but I did find some paintings and etchings. Note how many soldiers there are and how they are crammed in together. Many of these paintings and etchings show Nightingale with a lamp in her hand. And that's what she became known as. The Lady with the Lamp. Because she would make her rounds at night, long after the doctors had left, to check in on the patients. But even without the lamp, she's usually the glowing center of these paintings, like this one showing Nightingale receiving the wounded at the entrance to the hospital. Note the dead animals in the foreground there. A sanitary commission was sent to Skotari, and they found that the sewage pipes were clogged, and that the whole place sat on top of a literal cesspool of waste and filth. Among the many things they did to clean up the place was to remove the rotting carcasses of a dozen or so animals in and around the hospital. The soldiers didn't have clean bedsheets, or ventilation in the rooms, or even proper food. And these are conditions that are just unimaginable today. Nightingale came in with a plan to improve conditions, and by collecting data, she was able to show that her changes worked. With cleaning the place up, getting some fresh air moving, providing proper food, and you can see a drawing of the new hospital kitchen there, and just caring for the wounded soldiers, meant that they weren't all just going to die there, but could recover and return from the battlefield. Here's another chart she made, though it will look familiar. It shows the total number of deaths, but normalized to per 1,000 patients. That dashed circle near the center is the mortality rate for military hospitals near London. What this shows is that after they had made their changes, the death rate at Skotari was almost down to the same level that you would see back home in London, which is quite impressive for a field hospital out in the middle of nowhere. The chart is famous, and anything that gets talked about a lot tends to get misconstrued and misinterpreted. Perhaps the biggest one is around the name of the chart. It's sometimes called the coxcomb plot, and it's actually probably best known under that name. For all we know, Nightingale actually never named the chart, and the term coxcomb was only used by others later. The reason apparently being either that it was folded up like a coxcomb, or that it attracted attention like one. But either way, it's an odd name and kind of ugly. Nightingale's rose chart has a much nicer ring to it. The way the wedges are laid out is quite interesting too. They're not stacked on top of each other, but layered behind one another. That leads to issues in a few places where a smaller wedge might sit behind a larger one. Nightingale made sure to indicate when that was happening in the chart and also pointed it out in the caption. Also, this is of course not a pie chart. In a pie chart, the angle of the wedges around the circle would represent the data, and the radius would always be the same. And this is the opposite, where the angles are always the same, at least in the one that shows monthly data, and the area is scaled by changing the radius. It's also not a chart that was ever meant for analysis. Every now and again, I see people try to use it for some new data, and it's usually not very successful. It's a bit like Minara's chart of Napoleon's march. It works because it's unique and unusual. But that means you can't just use that same chart design for some other data and expect it to work. Especially if the goal is to be able to see small differences or compare numbers. It's not good for that. It was never meant to be. The chart was an addition to the tables in the report. It wasn't meant to replace them. The chart did become famous and kind of took on a life of its own fairly quickly though. Even during Nightingale's lifetime. Just a few years after it was first published, it was included in a different book as a little fold-out frontispiece without much explanation. Oh, it's Nightingale's world chart, of course. If you're looking for something to take away from this chart and this video, it's that Nightingale's chart worked because it was made for a very specific purpose. And that purpose was not to be able to analyze data, but to draw attention to large differences in important numbers. Nightingale knew what a bar chart was and she produced her share of bar, line, and area charts. But she clearly felt that she needed something less dry and more interesting to get people's attention. And the fact that we're still talking about it 160 years later shows that she was right. RJ Andrews is launching a book series on Kickstarter right now about Nightingale, Emma Willard, and Étienne-Jules Marais, three important figures from the early days of data visualization. I encourage you to check it out. The link is in the video description below. I also want to thank RJ for his help with the research for this video. And I'm linking to a great article that he wrote as well as a video of one of his talks below in the description as well. And you'll find links to more articles and blog posts to dive deeper into Nightingale's work, especially around charts and data. Florence Nightingale had a mission in life. And for her, it very literally was a divine calling. She was relentless in her work to improve people's lives, not just frontline soldiers. And she succeeded in reducing the need of suffering and death of countless people. The chart was helpful in that pursuit. But it was just a chart.