add Bell distribution
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- Dominant language
- C++
- Stars
- 839
- Forks
- 220
- Avg merge
- 2d 4h
- Merged PRs (30d)
- 14
Description
This feature request would add support for the Bell distribution. The Bell distribution is suitable for count data, has a single parameter, and can model overdispersed counts.
The PDF is:
$$\Pr (Y = k)=\frac{\alpha^ke^{-e^\alpha+1}B_k}{k!},\quad k = 0, 1, 2, \dots$$
where $\alpha>0$, and $B_k$ are the Bell numbers (i.e., unique partitions of a set).
The R package fndemarqui/bellreg has a Stan implementation.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing how existing probability distributions are organized in the Stan Math Library, then compare the requested formula with the Stan implementation in fndemarqui/bellreg. Done means Bell distribution support is added for the stated parameter and count domain, with behavior matching the supplied probability mass function.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- data
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100