Dataviz Universe

👋 Hi! About 10 years ago, I was a bioinformatician working on the wheat genome, feeling pretty lost about my career path. I had already started the R Graph Gallery and knew I loved data visualization, but I wasn’t sure where to take it. Curious about data science, I attended a conference and spoke with a hiring manager. When I mentioned my little side project in R, he laughed and said something I’ll never forget: "If you’re serious about dataviz, you need to learn D3.js." At the time, I had...

All my newsletter issues are now available online. Share them with a friend! 👋 Hi!Last week I shipped a whole new module about annotation in my matplotlib journey online course 🎉. I also shared with you a few thoughts about how legends should often be replaced by annotation.I shared this graph to illustrate my idea: Graph by Joseph Barbier for the Python Graph Gallery and Matplotlib Journey. Some people replied to me asking some legit questions about this stacked area graph (thanks! 🙏)Soooo,...

👋 Hi! You're now more than 9000 people reading this newsletter 😱. Thank you so much! 🙏🙏🙏If you want to share it with a friend, I just put together a (for now, ugly) homepage with all past issues. As always, today’s tip is short but powerful. Let’s talk about… The problem with legends Most dataviz libraries make it easy to add legends. That's great! Sometimes, they’re essential for understanding a chart. But most of the time? Legends are a hassle. Take this stacked area chart, for example:...

👋 Hey there! The sky is gray here, and I’ve got a delightful cup of tea in hand. The perfect setup to share another nugget of dataviz wisdom with you, all in under 3 minutes as usual. 🙂 If you work in data analytics or data visualization, there’s a debate you’re almost guaranteed to encounter at some point: Dual Y-Axis Charts: Good or Bad? 😱😱😱😱😱 For the uninitiated, a dual Y-axis chart uses 2 vertical axes on either side of the chart to represent 2 variables with distinct scales, plotted...

👋 Hi! This week, I'm writing the third module of my Matplotlib Journey project, and it's about a crucial yet often neglected part of data visualization: 🌈 Annotation ☀️ I like to think of annotations as what your chart would say if it could talk. Essentially, explaining to the reader what they need to understand. There are 2 main use-cases for annotations: 1️⃣ Annotation to Provide Context Let’s say you need to build a bubble plot showing the relationship between GDP per capita and life...

👋 Hi! Before we start, let me wish you my very best for 2025! I’m sure it’s going to be full of stunning charts, and I’m here to help you make that happen. 🙃 In case you forgot, you're currently reading Dataviz Universe, a newsletter where I share one short, to-the-point dataviz tip every week. Oh and I’m a real human called Yan Holtz on the other side! So feel free to hit reply anytime or ping me on LinkedIn! R² Is Not What It Seems R², or the coefficient of determination, is often seen as...

👋 Hi! Welcome to the last issue of 2024. Yes, time flies. 😳 Today, I’d like to share the story of the first impactful chart I ever made. It was about 12 years ago. I was in class with 20 other students, writing R code for a lesson on statistics and genomics. Instead of doing the assignment, I took a break, made this little Christmas tree, and sent it to everyone: It didn’t get me a good grade, but it gave everyone a good laugh! That's how it started A few months later, I graduated. Not...

👋 Hi there! I'm back from Paris where I gave a little talk about dataviz in front of real people. That was awesome, even though I didn't get time to see the Eiffel Tower 🙈. If you’re looking to level up your team’s dataviz skills, let me know! I gave 10 talks in 2024 and would love to do more in 2025. 🚀Anyway. As always, my goal this week is to share a quick dataviz tip you can add to your toolkit. The hardest thing: Colors 🎨 Last week I started a new section for my Matplotlib Journey...

👋 Hi there, It's been a windy weekend here. I had to squeeze in some windsurfing plus some work on matplotlib-journey.com, so I'm pretty late for this issue 🙈. But I couldn’t let the weekend slip by without delivering your weekly dose of dataviz tips. This week, let's tackle a common culprit that often makes my hair stand on end: Error bars I'm sure you know those little lines you often see at the top of bars in a chart. They’re meant to convey uncertainty and add context to the data. Without...

👋 Hey there, This week, I’ve got a little story for you. 🙂 A couple of years ago, at a dataviz conference in Portugal, the organizers ran a quick survey. They showed participants a list of chart types and asked two simple questions: 1️⃣ Have you heard of this chart?2️⃣ Have you ever created one in your career? 🧐 Here’s what they found By the way, this kind of graph is called a dumbbell or Cleveland plot 🙂 No surprises for the classics: nearly everyone recognized and had made a histogram. But...