Want to help?

Help expand the guide - share knowledge and code that can be reused across register-based research projects

Published

July 2, 2026

This guide is continuously evolving, and many researchers have solved the same classic problems each in their own project - without the code or the experience ever being shared. If we share, we all save time.

There are two kinds of contribution we are especially looking for: knowledge (recurring problems, methods and packages we should cover) and code (concrete, reusable solutions). You do not need anything finished - drafts and good pointers are gold too.

Share your knowledge

Where do register researchers keep hitting the same things? Point us in the right direction:

Recurring problems

Which pitfalls do you meet again and again? (immortal time, exclusion order, prevalent vs. incident, time-varying confounding …) - so we can describe them in one place.

Epidemiological methods

Designs, bias and analysis approaches specific to register data - and how to explain them simply for beginners.

Packages that already exist

Do you know an R package that solves a register problem? (e.g. heaven, Epi, MatchIt, EpiForsk, comorbidity …) Then we point to it instead of reinventing.

Share your code

Concrete, reusable solutions. It does not need to be validated - we are happy to work on from a draft:

Ethnicity

Deriving ethnicity/origin and generations from BEF/IEPE.

Medication and medication use

Exposure measures from LMDB: DDD, weighted use, PDC/MPR, insulin dosing, lag time and long-term prescriptions.

Family linkage

Linking parents, children and siblings via CPR/family id - e.g. to transfer exposures or covariates across generations.

Nordic Multimorbidity Index (NMI)

Computing NMI from LPR. We have a starter page - validated code and variants are very welcome.

Socioeconomic classification

Education, income and employment, e.g. by SEPLINE. We have a starter page - validated code welcome.

Time-varying variables

Variables that change over follow-up - blood tests, BMI, weight - in long format / intervals.

Simulated data

Simulated/synthetic datasets, so the guide’s code examples can be run without access to real DST data.

Note

It does not need to be finished or validated - we are happy to work further with drafts. If you have something else entirely that solves a general problem in register data, you are very welcome to get in touch as well.

How to contribute

Two ways - pick whichever suits you:

  • Email us (easiest): saras@clin.au.dk. Send code, a draft, or just an idea - we’ll add it. You need neither git nor GitHub.
  • Open a pull request on GitHub (if you’re comfortable with it): The guide’s source files live in a GitHub repository: github.com/steno-aarhus/registers-guide. Every page in the guide is a .qmd file, and the website itself is built automatically from them. A pull request is a proposal of concrete changes to those files that we can review and merge.
How do I send a pull request? (step by step)

A pull request is only a proposal - it is never merged automatically. We are notified, review the change, and merge it only once we have approved it. An outside contributor can therefore propose a change but cannot alter the page directly; only people we have explicitly given write access can merge. So nothing goes live behind our backs.

  1. Create a (free) GitHub account if you don’t have one.
  2. Find the file. Every page is a .qmd file under da/ (Danish) and en/ (English), and the filename is shown in the address bar: the page at .../en/09a_forstaa_lpr.html is the file en/09a_forstaa_lpr.qmd (the part before .html is the .qmd name, and da/en is the language folder). Just edit whichever language you’re comfortable with; we’ll take care of the other.
  3. Click the pencil icon (“Edit this file”) on the file. If you don’t have write access (outside contributors don’t), GitHub automatically makes a fork - your own copy of the project - and your changes are saved there, not in the original.
  4. Commit (“Commit changes”) and click “Create pull request”. To add a brand-new page instead, use “Add file” → “Create new file” at the top of the file list - that is sent as a pull request too.
  5. We review, comment if needed, and merge when it’s ready - and the website updates automatically.

Everything can be done in the browser; you don’t need to install git. If you prefer email, that’s perfectly fine.

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