[R] Genuine relative paths with R

Sun Oct 7 22:48:06 CEST 2018

On Sun, 7 Oct 2018, Olivier GIVAUDAN wrote:

> Hello Denes,
> 
> > Yes, the path to the "root" folder of your project. You seem to have a 
> really esoteric context if you want to run an R script without knowing 
> its path in the file system.
> 
> I don't have any esoteric context: I'm just looking for the most generic, automatic and reproducible solution.
> Of course you always know where an R script is located, nevertheless it doesn't imply you want to manually write its path in this
> R script. The issue is to have to hardcode an absolute path: I don't want that.
> 
> > Because it is extremely rare that someone - who uses R for what it is 
> worth and in a manner how R is supposed to be used - actually needs such 
> a function.
>

> First, the fact that it is rare doesn't mean this need is not legitimate 
> and relevant: it is needed to make R projects fully movable (i.e. 
> wherever you want). Second why a vast majority of languages does have 
> this feature and not R? Why is it useful in these languages and not in 
> R?

The R interpreter does not make assumptions about where the code it is 
running came from. You might be running it by using the source() function, 
or by using the Rscript program, or by R CMD BATCH, or using eval() on 
code you pasted together in an R function, or as byte-compiled code loaded 
from an RData file. That is, there is not always a file in a particular 
directory even involved in the executing code.

You also keep referring to "this feature" being in many languages, though 
you seem to be mistaken about most of them... in fact, they, too, know NOT 
where the script is but where the current directory is ($PWD is the same 
as getwd()) or where the compilation occurred (__FILE__ in C relates to 
the source code directory that is usually not where the executable is 
located and may not even exist on the computer it is running on).

I have already pointed out that the solution is to let the OS set the 
current directory. If you want the user to have access to R independent of 
your code, the easiest way to leave them in Rgui after your code is done 
is to use save.image() to create a "myApp.RData" file which can be 
double-clicked [1]. The double-clicking action by default (as defined by 
the installation of R) causes the operating system to set the current 
directory to the one containing the file you double-clicked on and then 
executes the Rgui program.

If you don't want the user to interact with your session, you can use the 
Rscript executable (also mentioned briefly at the bottom of [1]). In both 
cases, the user has (unknowingly) set the current directory before running 
your code, and there is no need to encode where the script is or was 
inside the script.

You can also create a windows shortcut to invoke Rscript yourself by 
bootstrapping the RData file and invoking the 
R.utils::createWindowsShortcut() [2] function.

However, by far the best approach is to teach your users to fish... if you 
give them an RStudio project directory they can double-click on the .Rproj 
file to set the current directory and enter the world of R.

[1] https://www.r-bloggers.com/look-ma-no-typing-autorunning-code-on-r-startup/
[2] https://cran.r-project.org/web/packages/R.utils/R.utils.pdf

End comment.

> Best regards,
> 
> Olivier
> 
> _________________________________________________________________________________________________________________________________
> De : D?nes T?th <toth.denes using kogentum.hu>
> Envoy? : samedi 6 octobre 2018 23:36
> ? : Olivier GIVAUDAN; Jeff Newmiller; r-help using r-project.org
> Objet : Re: [R] Genuine relative paths with R  
> Hi Olivier,
> 
> 
> On 10/07/2018 01:13 AM, Olivier GIVAUDAN wrote:
> > Hi Denes,
> >
> > Thank you for the possibility you shared: unfortunately it still uses
> > one hardcoded absolute path which I want to avoid.
> 
> Yes, the path to the "root" folder of your project. You seem to have a
> really esoteric context if you want to run an R script without knowing
> its path in the file system.
> 
> >
> > I just think that the solutions suggested are too complicated for my
> > simple need.
> >
> > The root cause being that R doesn't seem to have the Windows batch
> > equivalent of cd, or bash equivalent of $PWD, or PHP equivalent of __DIR__.
> > Hence the workarounds we are discussing.
> >
> > And finally we go back to my initial question: if such a function
> > doesn't exist in R, what are the reasons?
> 
> Because it is extremely rare that someone - who uses R for what it is
> worth and in a manner how R is supposed to be used - actually needs such
> a function.
> 
> Best,
> Denes
> 
> 
> 
> >
> > Best regards,
> >
> > Olivier
> > ------------------------------------------------------------------------
> > *De :* D?nes T?th <toth.denes using kogentum.hu>
> > *Envoy? :* samedi 6 octobre 2018 23:05
> > *?:* Olivier GIVAUDAN; Jeff Newmiller; r-help using r-project.org
> > *Objet :* Re: [R] Genuine relative paths with R
> > Hi Olivier,
> >
> > I really think that Ista and Jeff gave you plenty of useful options how
> > you can avoid using absolute paths.
> >
> > One more possibility: you can use `source()` with the chdir = TRUE
> > argument (see ?source). If you have a master script which sources other
> > files which are located in a fixed hierarchy relative to the location of
> > the master script, the only time when you have to use an absolute path
> > is when you source your master script, e.g.:
> > source("/my/path/to/master.R", chdir = TRUE)
> >
> > Inside the master script, you can then source the other scripts by
> > relative paths, define your 'data' folders relative to the master script
> > and let the other scripts use those data paths, etc.
> >
> > Best,
> > Denes
> >
> >
> > On 10/06/2018 11:36 PM, Olivier GIVAUDAN wrote:
> >> Hi Jeff,
> >>
> >> Thanks for sharing your workaround.
> >>
> >> I guess my last answer to Ista answers your question as well.
> >>
> >> To me this function (an equivalent of 'cd', say) should be platform-independent.
> >>
> >> Best regards,
> >>
> >> Olivier
> >>
> >> ________________________________
> >> De : Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
> >> Envoy??? : samedi 6 octobre 2018 19:31
> >> ??? : r-help using r-project.org; Olivier GIVAUDAN; r-help using r-project.org
> >> Objet : Re: [R] Genuine relative paths with R
> >>
> >> I stopped using hardcoded absolute paths inside R scripts years ago, and I suspect that is fairly common practice. That is, I
> almost never enter a path starting with "/" or "c:/" in an R script.
> >>
> >> The key concession you have to make is to start your R session in your working directory using OS-specific mechanisms, and
> then reference your code and data relative to that directory. RStudio project files offer one mechanism for doing this; using CD
> from  the OS command line is another, and using the file-browser
> > double-click mechanism on .RData files is another (though I prefer to
> > avoid that these days due to potential global environment contamination).
> >>
> >> Perhaps you can be more specific about what facilities you are expecting to find. You should also mention what OS you
> typically use and how you normally start R.
> >>
> >> On October 6, 2018 4:48:44 AM PDT, Olivier GIVAUDAN <olivier_givaudan using hotmail.com> wrote:
> >>> Dear R users,
> >>>
> >>> I would like to work with genuine relative paths in R for obvious
> >>> reasons: if I move all my scripts related to some project as a whole to
> >>> another location of my computer or someone else's computer, if want my
> >>> scripts to continue to run seamlessly.
> >>>
> >>> What I mean by "genuine" is that it should not be necessary to hardcode
> >>> one single absolute path (making the code obviously not "portable" - to
> >>> another place - anymore).
> >>>
> >>> For the time being, I found the following related posts, unfortunately
> >>> never conclusive or even somewhat off-topic:
> >>> https://stackoverflow.com/questions/1815606/rscript-determine-path-of-the-executing-script
> >>> https://stackoverflow.com/questions/47044068/get-the-path-of-current-script/47045368
> >>> http://r.789695.n4.nabble.com/Script-auto-detecting-its-own-path-td2719676.html
> >>>
> >>> So I found 2 workarounds, more or less satisfactory:
> >>>
> >>>
> >>> 1.  Either create a variable "ScriptPath" in the first lines of each of
> >>> my R scripts and run a batch (or shell, etc.) to replace every single
> >>> occurrence of "ScriptPath <-" by "ScriptPath <- [Absolute path of the R
> >>> script]" in all the R scripts located in the folder (and possibly
> >>> subfolders) of the batch file.
> >>> 2.  Or create an R project file with RStudio and use the package "here"
> >>> to get the absolute path of the R project file and put all the R
> >>> scripts related to this project in the R project directory, as often
> >>> recommended.
> >>>
> >>> But I am really wondering why R doesn't have (please tell me if I'm
> >>> wrong) this basic feature as many other languages have it (batch,
> >>> shell, C, LaTeX, SAS with macro-variables, etc.)?
> >>> Do you know whether the language will have this kind of function in a
> >>> near future? What are the obstacles / what is the reasoning for not
> >>> having it already?
> >>>
> >>> Do you know other workarounds?
> >>>
> >>> Best regards,
> >>>
> >>> Olivier
> >>>
> >>>        [[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
> >>> http://www.R-project.org/posting-guide.html
> >>> and provide commented, minimal, self-contained, reproducible code.
> >>
> >> --
> >> Sent from my phone. Please excuse my brevity.
> >>
> >>        [[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 http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> 
>

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