feat: add incrnanmmeanvar (moving mean/variance with NaN skipping) (fixes #5592)

[anoofmhd]

Resolves #5592.

Description

What is the purpose of this pull request?

This pull request:

• Adds a new incremental moving mean and variance accumulator: @stdlib/stats/incr/nanmmeanvar.

• This module behaves similarly to @stdlib/stats/incr/mmeanvar, but skips NaN values instead of propagating them.

• Includes implementation, tests, documentation, TypeScript definitions, REPL help file, benchmarks, and examples.

Related Issues

Does this pull request have any related issues?

This pull request has the following related issues:

• [RFC]: add stats/incr/nanmmeanvar #5592

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

No additional information.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

AI Assistance

When authoring the changes proposed in this PR, did you use any kind of AI assistance?

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

If you answered "yes" to using AI assistance, please provide a short disclosure indicating how you used AI assistance. This helps reviewers determine how much scrutiny to apply when reviewing your contribution. Example disclosures: "This PR was written primarily by Claude Code." or "I consulted ChatGPT to understand the codebase, but the proposed changes were fully authored manually by myself.".

I used ChatGPT to assist in understanding spec expectations and drafting documentation wording.
The implementation and test logic were written and verified manually.

---

@stdlib-js/reviewers

[stdlib-bot]

👋 Hi there! 👋

And thank you for opening your first pull request! We will review it shortly. 🏃 💨

Getting Started

• Please read our contributing guidelines if you haven't already.
• For development guidance, refer to the development guide.

Next Steps

1. A project maintainer will approve GitHub Actions workflows for your PR.
2. All CI checks must pass before your submission can be fully reviewed.
3. You'll need to address any failures in linting or unit tests.

Running Tests Locally

You can use make to run any of the CI commands locally from the root directory of the stdlib repository:

# Run tests for all packages in the math namespace:
make test TESTS_FILTER=".*/@stdlib/math/.*"

# Run benchmarks for a specific package:
make benchmark BENCHMARKS_FILTER=".*/@stdlib/math/base/special/sin/.*"

If you haven't heard back from us within two weeks, please ping us by tagging the "reviewers" team in a comment on this PR.

If you have any further questions while waiting for a response, please join our Gitter channel to chat with project maintainers and other community members.

We appreciate your contribution!

Documentation Links

• Contributing Guidelines
• Development Guide
• Gitter channel
• make rules for running examples
• make rules for running unit tests
• make rules for running benchmarks

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanmmeanvar	$\color{green}133/133$ $\color{green}+0.00%$	$\color{green}10/10$ $\color{green}+0.00%$	$\color{green}2/2$ $\color{green}+0.00%$	$\color{green}133/133$ $\color{green}+0.00%$

The above coverage report was generated for the changes in this PR.

[kgryte]

/stdlib update-copyright-years

[anoofmhd]

@Planeshifter @stdlib-bot @kgryte @rotu can you please review it and tell me if any changes needed or the PR is ready to merge.

[anoofmhd]

@kgryte Can you please review it and suggest me any changes needed.