BesselK continuous function
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- Dominant language
- C++
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Description
Description
In order to build robust count models based for example on SICHEL distribution, a continuous version of the BesselK function is needed (nu being real instead of int).
There is a tread here https://discourse.mc-stan.org/t/besselk-with-the-order-v-as-real-parameter/7417/4 but I thought to lounch a feature request since is quite a delicate math function (that is not working natively in log scale in the R version and therefore unstable)
For feature requests:
The code is present in R
https://stat.ethz.ch/R-manual/R-devel/library/base/html/Bessel.html
Expected Output
count ~ sichel(mu, sigma, nu)
Current Version:
v2.18.1
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 with the linked R Bessel documentation and the Discourse discussion about a real-valued BesselK order. Then locate the Stan Math entry point and relevant tests for BesselK, if present. Done means providing a continuous real-order BesselK suitable for the requested Sichel count-model use, including stable log-scale behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- backend
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100