From Data to Viz
A free decision tree that helps you pick the right chart from the shape of your data, with explanations of each chart type, its common mistakes and code examples. Ideal when you are unsure whether a bar, line, scatter or something else fits.
Guide
Other
Yan Holtz and Conor Healy
All
Free
What it is
From Data to Viz is a free website built by Yan Holtz, a data analyst, and Conor Healy, a designer. It classifies chart types by the kind of data you have: one or several numeric variables, categorical data, a mix of both, maps, networks and time series. You follow the branches of a decision tree from your data to a short list of suitable charts.
Each chart page explains what the chart is for, when it works, and the caveats and common mistakes, with links to code examples in R, Python, D3.js and React. The site also has a section on common data visualisation mistakes and a printable poster of the whole tree.
Why it is useful
Choosing a chart is where many dashboards go wrong: pies with twelve slices, dual axes that suggest a relationship that is not there, or a line chart for categories with no order. This site forces you to start from the data and the question, which is the right habit. The caveats pages are the most valuable part: read them for every chart type you use in a portfolio.
How to use it
- Write down what your data is: for example, "one numeric variable over time for five regions".
- Follow the tree to the suggested charts.
- Read the caveats for your choice, then build it in your own tool: Excel, Power BI, Tableau or Python.
- If the tree offers several options, prefer the simplest one your audience will read correctly. Bars and lines win most of the time.
Is it worth your time?
Yes. It takes minutes, it is free, and it improves every chart you make. It does not teach a tool; pair it with your tool's own training and with a guide to storytelling and presenting.
Free vs paid
The site is free. A printed poster is sold to support the project.
Common questions
Is it only for Python and R users? No. The decision tree and caveats are tool independent; the code links are optional.
Does it cover dashboards? Not layout. It covers choosing individual charts well, which is the foundation of a good dashboard.
Ready to start?
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Stuck on something specific?
Writing only gets you so far. If you want an answer to your situation rather than the general case, book a session and we will work through it together. Sessions are free for approved Sefism members, and a few slots open each week.
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