[R] Creating model formulas programmatically

[Gabor Grothendieck]

Another solution.  reformulate + substitute + as.formula:

substitute(~ (.)^2, list(. = reformulate(somenames)[[2]])) |> as.formula()

On Sat, Mar 29, 2025 at 5:31 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:
>
> Note: I am almost certain that this has been asked and answered here
> before, so my apologies for the redundant query.
>
> I also know that there are several packages that will do this, but I wish
> to do it using base R functions only (see below).
>
> The query: Suppose I have a character vector of names like this:
> somenames <- c("Heigh", "Ho", "Silver", "Away")
> (maybe dozens or hundreds: i.e. lots of names)
>
> Now suppose want to put these in a model formula like this:
> ~ (Heigh + Ho + Silver + Away)^2
>
> ... But **without** pasting them into a character vector and using
> parse(text = ...) , which, I grant, is sometimes the simplest way.
> Instead, I want to do it using Base R's computing on the language
> functions. I can do this with bquote() or substitute(), for example, like
> this:
>
> somenames <- c("Heigh", "Ho", "Silver", "Away")
> nms <- lapply(somenames, as.name)
> form <- nms[[1]]
> for(x in nms[-1])
>    form <<- bquote(.(form) + .(x), list(form = form, x = x))
> ## or form <<- substitute(form + x, list(form = form, x = x))
> form <- bquote(~ (.(form))^2, list(form =form))
>
> ## yielding
> > form
> ~(Heigh + Ho + Silver + Away)^2
>
> My question: Is there a simpler/slicker way to do this? This seems kinda
> kludgy, and I have the feeling that I'm missing something obviously better
> (in base R only; obviously better stuff is in various packages)
>
> Best to all,
> Bert
>
> "An educated person is one who can entertain new ideas, entertain others,
> and entertain herself."
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.



-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com