John, I believe the pieces you are missing are filed under 'computing on the language', 'passing unevaluated objects', and 'language objects'.
Forgive me if I belabor things you already know. lm, transform, and many other functions do their "magic" by operating on language objects. You might find a read of the `Computing on the Language' section in Venables and Pipley's `S Programmming' useful aa background. There are probably many blogs and other on-line resources, too. The unquoted things you want to operate on are language objects. deparse-ing those objects and trying to operate on character strings is one way to deal with such objects, but it can get messy. You might find that `transform.data.frame' provides a useful example of how to deal with language objects provided as arguments to a function. I suggest you try `debugonce' on lm and on `transform.data.frame'. Run an example of each and inspect each object created along the way. For lm, you should aim to understand everything through this line: mf <- eval(mf, parent.frame()) Getting familiar with `substitute', `match.call', `eval', and friends will help. HTH, Chuck p.s. It sounds like what you want to do is to extend `transform.data.frame' in some way. ?? > On Jun 1, 2019, at 6:43 PM, Sorkin, John <jsor...@som.umaryland.edu> wrote: > > Colleagues, > > Despite Bert having tried to help me, I am still unable to perform a simple > act with a function. I want to pass the names of the columns of a dataframe > along with the name of the dataframe, and use the parameters to allow the > function to access the dataframe and modify its contents. > > I apologize multiple postings regarding this question, but it is a > fundamental concept that one who wants to program in R needs to know. > > T ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
