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  • Megan Johanson

Magic is Something You Make

Every year, September makes me think of Harry Potter. September 1st is Back to Hogwarts Day, after all.

This September, I am combining two of my nerdiest interests: Harry Potter and Data Visualization. After all, you can find data anywhere, even at Hogwarts.

Below are 5 of the best Harry Potter visualizations I’ve seen (in no particular order), each using a unique visualization type and style, as well as my own humble contribution to the genre.

Each image is linked to the original source.

1. The Spells of Harry Potter (Interactive)

Author: Skyler Johnson

This interactive visualization is a dot plot showing each instance of every spell across all seven Harry Potter books. The books and corresponding dots are color coded.

This interactive and color-coded chart contains so much information it would take hours to wade through it all. And yet, it is easy and intuitive to browse spells of interest. I love the pop-up information that appears when you hover over any dot.

If I could make two changes, they would be to reorganize the colors so that the similar colors are not next to each other and that the dots would be lined up under the relevant books, not offset to the right of the labels. Although the color arrangement is beautiful, at a glance it can be hard to differentiate between the pink and the red, and the yellow and orange, which is made more confusing by the fact that the color dots do not stay within the color coded column for their respective books.

2. Spell the Spells (Interactive)

A static image of an interactive visualization. The visualization shows a dot plot where longer spells are higher and shorter spells are lower. The bottom shows a bar chart depicting how many spells start with each letter. Most spells start with A, P, R, C, or S.

This visualization takes a different perspective on analyzing the spells, a more linguistic approach. It is interactive so you can explore data by spell length and initial letter. I’ve always loved language so I like the ability to explore the spells and look for patterns.

The double y-axis could be a bit confusing because the charts are stacked on one another, but since the x-axis is the same for both charts it is still pretty easy to understand.

3. Emotional Arc of Harry Potter Books

Author: Computing for the Social Sciences at University of Chicago, with acknowledgement to Paul van der Laken

A small multiples bar chart, one for each of the seven Harry Potter books. Each bar represents a chapter and can be positive or negative, indicating positive or negative emotional scores. Most of the books have several positives and a few negatives. Deathly Hallows has far more negative chapters than positive.

This chart was found within an R learning exercise. During the analysis process, the author compared the number of positive and negative words in each book of the series. The author went even further to depict the emotional highs and lows of each book as bars charts, giving a big picture sense of the emotional arc of each story.

It isn’t entirely clear to me how the emotional score is calculated, but it is likely related to the positive and negative word usage calculations.

4. Character Presence Throughout Harry Potter and the Philosopher's Stone

Author: Alan Mathew

A chart with eight lines, one for each Harry, Ron, Hermione, Hagrid, Snape, Dumbledore, Malfoy, and Voldemort. Each line has a blue mark depicting a mention of that character in Harry Potter and the Philosopher's Stone. The timeline of the book goes from left to right across the page.

This is another big picture chart, because the individual data points are too numerous to meaningfully distinguish. What you can tell at a glance, is how frequently and roughly where in the timeline of the first book the main eight characters appear. If you are pretty familiar with the book you can even identify some groupings of data points. For example, Hagrid appears the most in the first third of the book, due to his role in Harry’s placement with the Dursleys and in transporting Harry from the guardianship of the Dursleys and into the wizarding world.

I really like this chart but I wish it had a title and maybe some key timeline annotations. It is embedded in an article with multiple Harry Potter themed visualizations and as a result is not labeled like a standalone chart usually would be.

5. Frequently Occurring Words in Harry Potter and the Deathly Hallows

Author: Haider Ali Punjabi

Word cloud in the shape of the Deathly Hallows symbol depicting the most frequently used words in Harry Potter and the Deathly Hallows. The largest words are Harry, Hermione, Ron, and Dumbledore.

This article presents several Harry Potter visualizations and I particularly enjoyed the custom word clouds displaying the most frequently used words in each book (the larger the word the more frequently it was used), in the shape that signifies the book.

With word clouds, it can be hard to draw specific comparisons. For example, is Ron's name bigger than Hermione's or are they equal? But for an overview of the main characters and themes of a book it does a good job, especially with the clever Harry Potter shaped word clouds. If you like this visualization, check out the link to see the word clouds for the other 6 books.

My Contribution: Were the Slytherins all Pure-bloods?

A table showing blood status and Hogwarts House of 54 characters from Harry Potter that attended Hogwarts, where blood status is known. Most Slytherins and Gryffindors are pure-blood, most Hufflepuffs and Ravenclaws are half-bloods. Slytherin is the only house with no known muggle-born students.

I was inspired by the September Storytelling with Data challenge to create a table. I broke many of my standard (read: professional) table rules to have a little more fun. Specifically, I used a question as the title and used the four house colors in the heat map rather than just one color.

I started with a dataset from Kaggle compiled by Gulsah Demiryurek. The data set included information on 140 named characters in the series. There were 97 characters who attended Hogwarts (at any time, not only as Harry's classmates) and of those only 54 had identified blood statuses.

I wanted to explore whether all known Slytherins were pure-bloods, if there were any muggle-born Slytherins, and which blood statuses were the most frequent in the other three houses.

As you can see, Slytherins were not exclusively pure-bloods, but there were no known muggle-borns. In addition, Hufflepuff and Ravenclaw are predominantly half-bloods.


There are a lot of great and diverse data visualizations from Harry Potter fans. Are there any stand-out visualizations from your favorite fictional world?

Please share!


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