Metric: reverse dependency count

[dgkf]

Description

A count of the number of packages that take the given package as a dependency.

Varies based on ...

• R environment: which repository urls are known to val.meter
• time

Discussion

Maybe we should call this the cran_reverse_dependencies_count so it's more concrete? It would still vary over time, but at least this would make it more clear which repos are being considered.

We could have a separate reverse_dependencies_count that is less clearly defined.

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^{requested by @aclark02-arcus in slack}

[aclark02-arcus]

Discussed on 12/11 weekly meeting

Three metrics are really being proposed here:

• cran_reverse_dependencies_count
• bioc_reverse_dependencies_count (@dgkf - we need a bioc_repo_resource created)
• repos_reverse_dependencies_count
  • this would look at any repositories that are available during your session just like available.packages()$repos does.
  • Also, @llrs-roche has done some prior work on this: https://repo.data.llrs.dev/reference/package_repos.html

[dominik-appsilon]

I started a draft PR #39 with implementation of the metrics. I still have a few questions about it that's why I haven't open it yet but the implementation is already functional and you can check that out.