paul-buerkner/brms

Conway-Maxwell-Poisson distribution

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#607 opened on Feb 22, 2019

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Description

The Conway-Maxwell-Poisson distribution (https://en.wikipedia.org/wiki/Conway%E2%80%93Maxwell%E2%80%93Poisson_distribution) is a generalization of the Poisson distribution that allows for both over- and underdispersion. There have been some attempts to get this distribution running in Stan, but I haven't seen one that works fast enough for most practical applications. Once we got such an implementation though, I think the distribution would make a very valuable addition to brms.

Contributor guide

Research direction
Study the Wikipedia article and existing Stan implementations. Implement the Conway Maxwell Poisson distribution in Stan following standard patterns, then integrate into brms by adding a new family and corresponding link functions.
Tech stack
r
Domain
databackend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
RStanBayesian statistics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35