YAN

HOLTZ

`Hello`I'm a dataviz engineer.

I build the custom charts off-the-shelf tools can't, with D3.js. Former Datadog engineer, creator of data-to-viz, the and many other dataviz references, read by 300,000 people a month.

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consulting

How I can help

I design and build bespoke, interactive data visualizations for the web: custom dashboards, data explorers and charts that off-the-shelf tools can't deliver. A modern stack (D3.js + React), tailored to your data and your users.

Got a dataset, a dashboard, or a Shiny app that deserves better? Tell me about it, I'd love to help make it shine.

Contact me

“Yan has taught me everything I know about data visualization! He taught my group how to display data in clever ways, and has been responsible for our recent interactive website related to psychiatric epidemiology.
He is a super-bright guy – I can highly recommend him!”

John McGrathSenior Researcher at the Queensland Brain Institute

free resources

You may already know my websites

I build free educational websites about data visualization. Together, they get about 300,000 page views a month.

Dataviz Inspiration

Hundreds of the best dataviz projects, to find ideas for your next chart.

Data to Viz

A classification of chart types based on your data format, with caveats to avoid.

Data to Art

A gallery of projects that turn data into stunning, more or less abstract visuals.

The Dataviz Decision Tree

Which chart fits your data? A poster classifying chart types by input data format.

about

My story

My first chart was a Christmas tree, drawn in R during a genetics class instead of doing the assignment. It didn't get me a good grade, but it got me hooked.

After my master's, I crossed the Atlantic on a sailing boat. Halfway, that same teacher emailed me a job offer. I became a bioinformatician studying the wheat genome, and my favourite part was always the end of the pipeline: the chart.

On nights and weekends, I built the R Graph Gallery. It grew enough to land me a job at the Queensland Brain Institute in Australia, where I created data-to-viz.com. That led to Datadog, where I spent five years as a software engineer and fell for D3.js.

In 2024, my side projects had grown enough for me to go independent. I now build custom dataviz for clients, teach, and write a weekly newsletter. And I've never had to apply for a job.

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teaching

Online courses

I've built 4 online courses, now followed by more than 2,000 students. Each one is hands-on and interactive, and focuses on one tool so you can go deep. Pick the one that matches your stack.

D3 ❤️ React

Interactive data visualization for the web, with D3.js and React.

My flagship course: build truly custom charts, the reliable way in the AI era.

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Matplotlib Journey

Python dataviz with Matplotlib.

An all-in-one, highly interactive course to become a Matplotlib dataviz expert.

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ggplot2 uncharted

Dataviz with R and ggplot2.

Master ggplot2 through coding, design and AI workflows. With Cédric Scherer.

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Productive R Workflow

Clean, reproducible R projects.

Work faster and cleaner in R: turn messy scripts into reproducible projects.

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projects

Portfolio

Client work, educational projects, data explorations and dataviz essays. Here is a glimpse of what I've built over the last few years, so you can see the kind of work I do.