Interactive data visualization
for the web.

Trainings for teams

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I frequently deliver tailored trainings to teams on a range of dataviz topics — from choosing the right chart and design principles to hands-on coding sessions. I work across the whole stack: D3.js and React for the web, but also R and Python. Every session is adapted to your team's level and goals.

My flagship course

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d3-loves-react.com — learn to build modern, interactive data visualizations for the web by combining the power of D3.js with the comfort of React. In the AI era, this is the most reliable way to produce truly custom, high-impact charts, and this course takes you from zero to confident.

Other courses

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• Productive R Workflow — work faster and cleaner in R.
• ggplot2 uncharted — master data visualization with ggplot2.
• Matplotlib Journey — become fluent in Python dataviz with Matplotlib.

I can help you if

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• You're seeking a dynamic speaker for a conference on data science, software engineering, or data visualization.
• You're looking to elevate the skills of your team members.

Example:

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• Choosing the right chart for your data: the process to build an insightful graph. Invited speaker for the MIT.
• R in the dataviz universe: a tour of the dataviz tool ecosystem. Keynote at the R french national conference.
• Building great charts with R. Talk for the Advanced Data and Information Visualization course of Harvard university.

Contact me

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Tell me more about your project at yan.holtz.data@gmail.com to see if we can work together.

I can help you for

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• Exploratory analysis of a dataset.
• Creation of clean and reproducible reports using R Markdown.
• Application of statistical methods on your dataset.
• Creation of custom scripts for analysing your data automatically

Example:

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• I'm the author of several scientific publications where I was in charge to explore and understand complex dataset in order to answer scientific questions.
• I recovered information about crypto currency prices on different exchanges and explored the data looking for arbitrage opportunities.

Contact me

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Tell me more about your project at yan.holtz.data@gmail.com to see if we can work together.

I can help you with:

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• Creation and review of graphs for scientific publications.
• Development of data-centric applications using R Shiny, JavaScript, and React.
• Design of custom web-based data visualizations using d3.js.

Example:

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• A Shiny App describing research results on mental disorders comorbidity.
• Data to viz: a decision tree leading to the most appropriate chart type for your data.
• See many more examples in the portfolio section of this website.

Contact me

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Tell me more about your project at yan.holtz.data@gmail.com to see if we can work together.

Description

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A group of researcher from the Institute of Molecular Bioscience investigated the geographic clustering of genetic variants that influence complex traits and disease risk in a sample of ~450,000 individuals from Great Britain.

I built a web application that goes in support of the paper intitled Genetic Consequences of Social Stratification in Great Britain.

The shiny application allows to visualize the geographic distribution of any trait. It allows to custom color scales, region shape and to apply a cartogram algorithm to the map. Moreover, the tool allows one to upload its own data to benefit this dataviz tool.

Read more

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The web application is available online. You can read the scientific paper on BioArXiv. The source code of the project are of course on Github.

Description

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Lumo is a custom template for Quarto. It will make your report looks good and minilasit instantly.

It basically applies a lot of my Quarto tips instantly for you!

Description

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The Pacific Dataviz Challenge is a competition organized to promote data visualization skills in the Pacific region.

I won the 2024 edition with a project on gender inequality in the Pacific region.

I made the application in 48 hours, using Javascript, React and D3.js.

Read more

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The web application is available online. You can read the code on Github.

Description

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After years teaching data visualization, I realised most of my students struggle with their design eye.

They get very good at coding and respecting dataviz best practices. But drawing something that looks polished and professional is hard.

So I built a little game where students must find the better looking chart! It makes them learn design principles along the way.

Description

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Building and comparing genetic maps between several populations is a common task for geneticists.

We've created an online tool allowing to upload your maps and characterize and visualize them. Several interactive graphs are available with export options and more. The tool was created using R and Shiny, plus several Html widgets for interactivity.

Read more

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The web application is available online. You can read the scientific paper on Bioinformatics. The source code of the project are on Github.

Description

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Comorbidity is defined as the presence of 1 or more disorders in relation to an index disorder. I've been involved in a project with the Queensland Brain Institute (Australia) and the University of Aarhus (Denmark) to build an interactive website allowing to explore the discovered patterns of comorbidity between mental disorders.

The online tool goes with the publication in Jama Psychiatry. Several interactive graphs are available with export options and more. The tool was created using R and Shiny, plus several Html widgets for interactivity.

Read more

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The web application is available online. You can read the scientific paper on Bioinformatics. The source code of the project are on Github.

Description

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Terres Inovia is a French company carrying out applied research on oilseed plants and protein crop. It phenotypes the main varieties of 20 crop species in many locations for several traits every year. This information is stored in a massive SQL database.

I created a dashboard allowing to explore these data. It allows to quickly understand what variety performs well in what kind of environmental condition. It thus has a direct impact on advices provided to farmer in France.

The dashboard was created using R and Shiny. It requires several HTML widgets to create interactive graphs, and specific packages to interact with the database. Here is a screenshot of the welcome page of the application:

Read more

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I can't provide more information on this project for privacy reasons.

Description

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Google Scholar is a service that provides any researchers list of publication. I made a script that harvest this information on the web using R. It then take the list of all co-authors and check for each pair if they have published a paper together.

The network information is then visualized using static graphs with R, and also using interactive version thanks to d3.js

Read more

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Data mining part of the pipeline is available on github. Visualizations are used as example in my other projects: static charts in data to viz, interactive ones in the d3 graph gallery.

Description

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The GreenTech challenge is a Dataviz competition launched by the French Ministery of environment that took place in 2017. A huge dataset concerning pesticides in France has been released, and the goal was to build innovative visualizations to sensibilize and inform citizen concerning the french situation over the past 6 Years.

We decided to make a team of 4 friends and built a ShinyApp that allows to efficiently explore this dataset. The app is composed by several sheets, each targeting a specific theme. This tool should allow you to understand what happens in your neighbourhood and in the entire country. It is also studied to improve your genereal knowledge concerning pesticides.

Read more

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See the associated github repository for more information and source code of the project.

Description

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UNICS is a web app that helps you computing the standard error of allele frequency estimations of future pool-sequencing experiments based on different parameters. You can use it trough the online version and read the related publication.

Application looks like this:

Read more

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See the associated github repository for more information and source code of the project.

Description

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I created an R script that recovers all tweets containing the hashtags #surf and run it on a webserver for about 9 months. I recovered more than 400k tweets. Some of them being geolocalized for both home and current location, it is possible to deduce where surfers travel.

Here is an overview of the result:

Read more

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See the dedicated page in data-to-viz.com that tells more about this project, with explanation on how to build a connection map.

Description

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Matplotlib is a powerful Python library for data visualization, but its API can be overwhelming. This interactive tool lets you explore all the available methods, see examples, and understand how to use them effectively.

Perfect for both beginners and advanced users who want to master Matplotlib's capabilities.

Read more

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Try the interactive explorer online. The project is part of the Matplotlib Journey course.

Description

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Quarto is a powerful tool for creating dynamic documents, but mastering its full potential requires knowing the right tricks.

I made a curated list with the most useful tips to make your Quarto reports more beautiful, functional, and professional.

Read more

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Explore the full list of Quarto tips and tricks here. This resource is part of the Productive R Workflow course.

Description

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Dive deep into the 4 main types of Data Professionals: Data Engineer, Machine Learning Engineer, Data Scientist, and Data Analyst. This interactive app lets you explore their main required competencies, salary ranges, and popularity trends.

Built with React and D3.js, the project features animated radar, line, and lollipop charts. Switch between roles to see smooth transitions and compare skills, salaries, and job popularity over time.