Rsquared with weights

[newville]

This fixes #921

Type of Changes

• [x] Bug fix
• [ ] New feature
• [ ] Refactoring / maintenance
• [ ] Documentation / examples

Tested on

Python: 3.11.5 | packaged by conda-forge | (main, Aug 27 2023, 03:35:23) [Clang 15.0.7 ] lmfit: 1.2.2.post11+g5a081c5.d20231107, scipy: 1.11.3, numpy: 1.26.0, asteval: 0.9.31, uncertainties: 3.1.7

Verification

Have you

• [ ] included docstrings that follow PEP 257?
• [x] referenced existing Issue and/or provided relevant link to mailing list?
• [x] verified that existing tests pass locally?
• [ ] verified that the documentation builds locally?
• [ ] squashed/minimized your commits and written descriptive commit messages?
• [x] added or updated existing tests to cover the changes?
• [ ] updated the documentation and/or added an entry to the release notes (doc/whatsnew.rst)?
• [ ] added an example?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (c415990) 93.23% compared to head (ccc7755) 93.23%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #923 +/- ## ======================================= Coverage 93.23% 93.23% ======================================= Files 10 10 Lines 3697 3697 ======================================= Hits 3447 3447 Misses 250 250 ``` | [Files](https://app.codecov.io/gh/lmfit/lmfit-py/pull/923?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=lmfit) | Coverage Δ | | |---|---|---| | [lmfit/model.py](https://app.codecov.io/gh/lmfit/lmfit-py/pull/923?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=lmfit#diff-bG1maXQvbW9kZWwucHk=) | `91.25% <100.00%> (ø)` | |

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[newville]

@reneeotten Yeah, that was pretty bad!! I'll merge this. It's been a few months since 1.2.2. It might be good to push out 1.2.3 soonish, but I'm not sure I'll have the time to do that this week and next week will be busier for me, but hopefully by early December.