Introduction to box plots
Box plots, also known as box-and-whisker diagrams, are a great way to get a quick overview of how your data is spread out. They help you spot patterns, trends, and anything unusual at a glance. They’re particularly useful for comparing different groups or categories, allowing you to quickly see how each one varies in terms of distribution and outliers.
Box plots are available as a starting point in Flourish, so creating and publishing them online is now as easy as uploading a spreadsheet! Like every Flourish visualization, our box plots are mobile-friendly, animated and free to make and publish.
Anatomy of a box plot
In a box plot, the box itself highlights the middle range of your data and divides the data into sections called quartiles. The line inside each box marks the median (the middle value). The “whiskers” extend out to show the overall range, and any unusual data points, called outliers, appear as dots outside the whiskers.
To create a box plot, you need one axis for numerical (like values or measurements), and one axis for categorical data.
Flourish box plots
The box plot starting point in Flourish, part of our Scatter plot template, comes packed with handy features. One standout advantage is that they automatically calculate and display key values like the median and range, so all you need is to upload your data! See the example below to learn more.
Flourish box plots can also be displayed either horizontally or vertically, making them adaptable for different screen sizes, including mobile. For the whiskers, Flourish allows you to set a maximum distance they can extend beyond the box, or remove them altogether if needed. Typically, whiskers shouldn’t extend more than 1.5 times the range between the first and third quartiles (also called IQR). Any data points beyond that are marked as outliers.
Finally, you can add an interactive filter, letting users easily compare categories. These can significantly improve your data storytelling — explore other examples of how animations can take your visualizations to the next level.
Data structure for a box plot
To create a box plot, upload a dataset with one categorical and one numerical column for your X and Y axis, and add optional columns that determine chart properties such as dot color, size or filter.
How you set up your columns in the Data tab decides whether your box plot is vertical or horizontal. To make a horizontal box plot, pick a category for the Y axis and a number (like a value or measurement) for the X axis. For a vertical layout, switch your X and Y values.
A
B
C
D
E
F
Animal
Movement type
Highspeed
Weight (to be filtered by)
Continent (to be colored by)
Image
Aligator
Swimming
32
100-1000kg
North America
[URL]
Black mamba
Running
24
1-10kg
Africa
[URL]
Great tit
Flying
33
<1kg
Europe
[URL]
Hippopotamus
Running
48
Over 1000kg
Africa
[URL]
The Scatter template also supports images. In each row cell you can right click/double click and select Upload file to upload the image you wish to use for that point. Alternatively, you can supply a URL from a public source, such as Wikimedia Commons.
Resources
Here are some resources to help you get started with box plots:
