Fix some lints in the R folder

[etiennebacher]

Hello, I'm building a new package to find and automatically fix lints in R code: flint.

I'm using real-life, large packages to check its performance and ggplot2 is one of them. Since I already test on this, there's no additional cost for me in proposing those changes.

FYI, those changes were all generated by flint::fix_dir("R").

There are many changes but most of them are trivial:

• replace any(is.na()) by anyNA()
• replace the = assignment by <- (since both are used across the codebase, I guess <- should be the default)
• add a leading 0 to decimal (e.g .1 -> 0.1)

and a few other things.

flint is quite new and linter rules are necessarily a bit opinionated, so some of those changes might not be to your taste, but I'd be happy to have some feedback on this.

[teunbrand]

Thanks Etienne, these look all great to me.
I was in the progress of preparing a big linting PR as well so this is great to see.

An additional thing ggplot2 might still want to replace is seq_len(nrow(x)) with vctrs::vec_seq_along(x), but that perhaps not for this PR.

[etiennebacher]

An additional thing ggplot2 might still want to replace is seq_len(nrow(x)) with vctrs::vec_seq_along(x), but that perhaps not for this PR.

I think this would be a perfect case study for setup_flint(), which creates a flint folder where you can add custom rules used by flint or deactivate parts of the built-in rules. Would you be open to a PR with this? Not everything is fleshed out on how a flint update would affect the flint folder, so you might want to wait for a more stable version of flint.

[teunbrand]

Would you be open to a PR with this?

ggplot2 doesn't do any automatic linting and I don't think we're likely to change that, so we'll gladly accept the improvements presented in this PR but are hesitant towards any deeper integration at this point.

[teunbrand]

I'm going to merge this quickly before I bestow any merge conflicts on this PR, thanks for this!