ENH: add dtype option to numpy.lib.function_base.cov and corrcoef

[lschwetlick]

I tried to implement the changes suggested in Issue #17395, by adding a dtype keyword to the cov and corrcoef functions in numpy/lib/function_base.py. I also wrote tests for the changes.

Closes #17395

[eric-wieser]

This generally looks good, thanks for the contribution. Two more things:

• The dtype argument needs documenting, and should include .. versionadded:: 1.20.0
• We should maybe add a release note in the upcoming_changes folder.

[lschwetlick]

Sure, I can certainly do that. I left it out initially to see whether there was interest in actually merging the PR. Thank you for reviewing so quickly @eric-wieser !

[eric-wieser]

This probably doesn't need to hit the mailing list, but I'll leave it for another maintainer to give a second opinion on. Thanks for the rapid iteration.

[lschwetlick]

Happy to help!

Its a bit silly maybe but if its no trouble, could you add the label "hacktoberfest-accepted" to the PR? They changed the rules to prevent spam.

[eric-wieser]

@lschwetlick, there's no need for me to do that according to your link, my approval above is enough.

What does matter is if the repo has a hacktoberfest topic, which it currently does not. I'd be happy to add it to make this PR count, but I worry that we might draw spam attention as well.

[lschwetlick]

Yup, I get it. I mainly liked the gamification aspect as a motivator. Good use of my time anyway :)

[rossbar]

LGTM as well, seems like a nice improvement. Thanks @lschwetlick !

[rossbar]

I've updated the docstring wording based on @seberg 's comment (and undid my test changes since I was in there). I'll merge once the CI's done - I don't want to let wording block this nice new feature (thanks @lschwetlick !) We can always revisit the docs later to improve the wording or add more explanation if needed.

[eric-wieser]

Added the hacktoberfest-accepted label, since I think @mattip said that was preferable to the repo topic. Apologies if it's too late to make a difference!

[lschwetlick]

Nice, thank you @eric-wieser !