logo
Jeroen Janssens

Jeroen Janssens

Head of Developer Relations

Jeroen Janssens, PhD, is Head of Developer Relations at Posit, PBC. His expertise lies in visualizing data, implementing machine learning models, and building solutions using Python, R, JavaScript, and Bash. He’s passionate about open source and sharing knowledge. He’s the author of Python Polars: The Definitive Guide (O’Reilly, 2025) and Data Science at the Command Line (O’Reilly, 2021). Jeroen holds a PhD in machine learning from Tilburg University and an MSc in artificial intelligence from Maastricht University. He lives with his wife and two kids in Rotterdam, the Netherlands.

Posts and Resources by Jeroen Janssens

Seeing Beyond Statistics: Anscombe's Quartet and the Power of Graphs

Seeing Beyond Statistics: Anscombe’s Quartet and the Power of Graphs

In 1973, statistician Francis Anscombe challenged the commonly held belief that “numerical calculations are exact, but graphs are rough” (Anscombe, 1973). His strategy was to manually construct four small datasets—now known as Anscombe’s Quartet—that have different distributions but nearly identical descriptive statistics. It’s perhaps the best argument for visualizing data. In this notebook we replicate his paper by using Plotnine to visualize those datasets and Polars to verify their descriptive statistics. More specifically, we:
5 minutes to read