Jeff Thanks for your insights. I suspected that this was the case but I was hoping for a work-around. Regardless, I have modified the code so that the source() command is no longer in a function — all the pre- and post-commands are now in two functions, executed before and after the source command. Problem solved.
Dennis Dennis Fisher MD P < (The "P Less Than" Company) Phone / Fax: 1-866-PLessThan (1-866-753-7784) www.PLessThan.com > On May 14, 2016, at 9:45 AM, Jeff Newmiller <jdnew...@dcn.davis.ca.us> wrote: > > I think you have boxed yourself into a corner, much like someone painting the > floor and failing to work their way toward an exit. > > The whole premise that you will call "unknown code" that does "unknown > things" that change the global environment is a maintenance disaster. Give up > on at least one of these requirements. > > Think of the "lm" function. It returns a list of related results, augmented > with a "class" attribute so that methods like "print.lm" and "summary.lm" > will work. The actions performed need not be reviewed in detail if the user > knows what to do with the returned object. The "class" attribute is a bit of > syntactic sugar, but the concept of putting your results into a list that the > caller doesn't have to mix items in with their own is critical. > > Using <<- has to be handled in a very controlled manner... wonton (as in > "users will change my variables this way") use of that operator will > inevitably lead to surprises and puzzlement later. > > I also happen to think that standardizing on calling "source" inside > functions is a big mistake... the functions defined by the user should be > setup and handed off to your "master architecture" code as parameters or > elements within lists that are parameters. > > On Sat, 14 May 2016, Fisher Dennis wrote: > >> R 3.2.4 >> OS X and Windows >> >> Colleagues, >> >> I distribute some code to co-workers and I am trying to simplify their task. >> The issue is as follows: >> >> 1. The code automates an extensive set of processes. Many of the steps are >> standardized. However, some of the steps may require that users write >> snippets of code, stored in R scripts. >> >> 2. If users write their own code, it might appear in files named >> UserCode1.R, UserCode2.R, etc.. The master code checks for the existence of >> this code, then executes >> source(?/path/to/UserCode1.R?) >> This can occur at many different points in the master code (each time >> sourcing a different file). In addition to the command above, there are a >> variety of other commands testing whether the file exists and whether it >> contains certain commands that I don?t allow the user to execute. >> In order to simplify the code, these commands are embedded in a function >> (which I will call MODIFYCODE for the moment). >> >> 3. Assume that an object within the master code is named TEMP. The user >> might add a column to TEMP. Since this occurs within a function, there are >> two ways to get this modification back to the original environment: >> a. within the function: TEMP <<- TEMP >> b. use the return value from the function: >> TEMP <- MODIFYCODE() >> >> 4. There are disadvantages to each of these: >> a. The user needs to know that the ?<<-? command must be invoked. If >> they don?t do so, the changes within the function are not available in the >> master environment >> b. I don?t know what code will be written by the user, i.e., they >> might manipulate TEMP or they might create a new object or something else. >> So, I don?t know a priori what to return. >> >> So, my question is: is there some way to manipulate environments such that >> the changes within the function are AUTOMATICALLY transferred to the >> environment outside the function? >> >> Dennis >> >> Dennis Fisher MD >> P < (The "P Less Than" Company) >> Phone / Fax: 1-866-PLessThan (1-866-753-7784) >> www.PLessThan.com <http://www.plessthan.com/> >> >> >> >> >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> 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. > > --------------------------------------------------------------------------- > Jeff Newmiller The ..... ..... Go Live... > DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... > Live: OO#.. Dead: OO#.. Playing > Research Engineer (Solar/Batteries O.O#. #.O#. with > /Software/Embedded Controllers) .OO#. .OO#. rocks...1k > --------------------------------------------------------------------------- ______________________________________________ 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.
