stan-dev / stan-dev/rstanarm

stan_gamm4: bug with polynomial parameter

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bug
Dominant language
R
Stars
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Forks
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No merged PRs in 30d

Description

rstanarm appears to fail when entering a polynomial parameter:

This works

rstanarm::stan_gamm4(Sepal.Width ~ Sepal.Length + s(Petal.Width), random=~(1|Species), data=iris)

This doesn't

rstanarm::stan_gamm4(Sepal.Width ~ poly(Sepal.Length, 2) + s(Petal.Width), random=~(1|Species), data=iris)
Error in poly(Sepal.Length, 2) : object 'Sepal.Length' not found

Note that the same using gamm4 works:

gamm4::gamm4(Sepal.Width ~ poly(Sepal.Length, 2) + s(Petal.Width), random=~(1|Species), data=iris)

Is there a way to fix it?

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start at the stan_gamm4 entry point and reproduce the failing iris example with poly(Sepal.Length, 2), then compare it with the working gamm4 call. Trace how the formula is evaluated and identify why Sepal.Length is unavailable; done means the polynomial example works and a regression test covers it.

Written by the indexing model from the issue text.

Assessment

Tech stack
r
Domain
data
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
45/100

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