Add Zenodo DOI for Citable Releases

Also see #68.

Summary

Set up Zenodo integration to automatically generate DOIs (Digital Object Identifiers) for each CausalPy release. This enables proper academic citation and long-term archival of the software.

Why This Matters

• Academic credibility: DOIs are the standard for citing research software
• Discoverability: Zenodo records are indexed by academic search engines
• Permanence: Archives are preserved long-term, even if GitHub changes
• Citation tracking: See how and where CausalPy is being cited

Implementation Steps

Step 1: Connect GitHub to Zenodo (One-time setup, ~5 min)

1. Go to Zenodo's GitHub settings page
2. Log in with GitHub credentials (needs to be an org admin or have appropriate permissions)
3. Authorize Zenodo to access pymc-labs repositories
4. Toggle the switch to "On" for pymc-labs/CausalPy

Step 2: Create the First Release with Zenodo

1. Create a new GitHub release as normal (e.g., v0.7.0)
2. Zenodo automatically detects the release and:
   • Archives the repository at that state
   • Assigns a unique DOI to that version
   • Creates a "Concept DOI" that always points to the latest version
3. This process takes a few minutes

Step 3: Add DOI Badge to README

After the first release is processed:

1. Go to the Zenodo record for CausalPy
2. Click on the DOI badge to get the Markdown code
3. Add to README.md badges section:

[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.XXXXXXX.svg)](https://doi.org/10.5281/zenodo.XXXXXXX)

Important: Use the Concept DOI (not the version-specific DOI). The Concept DOI always resolves to the latest version, so the badge never needs updating.

Step 4: Update Citation Section

Update the "Citing CausalPy" section in README.md to include the DOI:

@software{causalpy,
  author = {{PyMC Labs}},
  title = {CausalPy: Causal inference for quasi-experiments in Python},
  url = {https://github.com/pymc-labs/CausalPy},
  doi = {10.5281/zenodo.XXXXXXX},
  year = {2026}
}

Step 5 (Optional): Add CITATION.cff File

GitHub natively supports CITATION.cff files, which provide structured citation metadata. When present, GitHub shows a "Cite this repository" button.

Create CITATION.cff in the repository root:

cff-version: 1.2.0
message: "If you use this software, please cite it as below."
type: software
title: "CausalPy: Causal inference for quasi-experiments in Python"
authors:
  - name: "PyMC Labs"
repository-code: "https://github.com/pymc-labs/CausalPy"
url: "https://causalpy.readthedocs.io"
license: Apache-2.0
doi: 10.5281/zenodo.XXXXXXX

Concept DOI vs Version DOI

Zenodo provides two types of DOIs:

Type	Example	Use Case
Concept DOI	10.5281/zenodo.1234567	Always points to latest version. Use in README badge.
Version DOI	10.5281/zenodo.1234568	Points to specific version. Use when citing a specific release in papers.

The Concept DOI is ideal for the badge because it never needs updating.

Automation Considerations

What's automatic:

• DOI generation for each new release
• Archival of repository state
• Linking between versions

What's manual:

• Initial setup (one-time)
• Adding badge to README (one-time if using Concept DOI)
• Updating CITATION.cff with new DOI (one-time if using Concept DOI)

Optional automation:
A GitHub Action could be created to update version-specific DOIs in documentation, but this is likely overkill if using the Concept DOI.

Acceptance Criteria

• Zenodo integration enabled for pymc-labs/CausalPy
• First release archived with DOI assigned
• DOI badge added to README.md (using Concept DOI)
• BibTeX citation updated with DOI
• (Optional) CITATION.cff file added

References

• GitHub: Referencing and citing content
• Zenodo GitHub integration
• CITATION.cff format

Start by reading the README.md badges and “Citing CausalPy” sections, then review the repository’s GitHub release settings and Zenodo integration requirements. Enable the integration, archive a release, and use the resulting Concept DOI in README.md; add CITATION.cff if included in scope. Done means the acceptance checklist is satisfied and the DOI resolves correctly.