scverse / scverse/scanpy

Potential error in scanpy.tl.rank_genes_groups?

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Description

Please make sure these conditions are met
  • I have checked that this issue has not already been reported.
  • I have confirmed this bug exists on the latest version of scanpy.
  • (optional) I have confirmed this bug exists on the master branch of scanpy.
What happened?

Hi,

this recent preprint https://www.biorxiv.org/content/biorxiv/early/2023/08/20/2023.07.20.549945/DC1/embed/media-1.pdf?download=true

claims that there is an issue with
https://github.com/scverse/scanpy/blob/master/scanpy/tools/_rank_genes_groups.py#L419C1-L423C48

that reportedly leads to log-fold changes of 30 or -30 when gene expression is 0 in a cluster.

What do you think about this?

Minimal code sample
https://github.com/scverse/scanpy/blob/master/scanpy/tools/_rank_genes_groups.py#L419C1-L423C48
Error output

No response

Versions

master

Contributor guide

Open the contributing guide

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 by reading the referenced section of scanpy/tools/_rank_genes_groups.py and the linked preprint's claim about zero expression and log-fold changes. Reproduce the behavior with a minimal Scanpy example, since the issue provides no executable sample. Done means determining whether the reported values are erroneous and documenting the result or identifying the needed follow-up.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
bioinformatics
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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