NoviceDeveloperResources

Barry Zeeberg [aut, cre]

2024-01-30

 

 

Barry Zeeberg


 

MOTIVATION

This is a short manual that I wish I had when I was trying to figure out how to get started, and how to continue. The vocabulary that more experienced developers use has terminology that is not that helpful to an uninitiated novice. And there are several types of objects that reside in various obscure places on your computer, and a collection of commands to view or operate on these objects. Finally, the commands can be issued from 4 different places: The UNIX terminal window (e.g., on Macintosh computers), the R Console window, the R Studio menus, or the R Studio console. I will focus here on operating and navigating within the R Console window, which can be considered to be necessary and sufficient.

BASIC COMMANDS

A package is a unified integrated set of functions and objects that can be installed by users of R. A few of these automatically come along with the R program, but the others must be installed (usually from the CRAN repository, which you can browse through to find the package that you seek) by issuing

install.packages(“package-name”)

The collection of your installed packages is called a library, residing in e.g., /Library/Frameworks/R.framework/Versions/4.3-arm64/Resources/library. All of your installed packages can be viewed by issuing

library()

The output (Figure 1) can be a very long list, if you have been doing this for a while, and is printed out in a separate window, presumably to avoid cluttering up the main R Console window.

Figure 1. Output of library() command.

You can confirm that you have in fact successfully installed the package into the library by checking that it has the expected creation time (Figure 1a). I mention this because I have had problems replacing an older version of the package with the newer version when using the R Studio “Clean and Install” button. Fortunately this problem does not occur with checkBuildInstallSourcePackage() (see below).

Figure 1a. Creation time of installed package in the library

The installed libraries are not directly available for your use, until you have attached them or (in different words for the same thing) loaded them to your search path. Here we encounter the confusing syntax: you attach a package by issuing

library(package-name)

It would make more sense for the command to be something like attach(package-name), since, as just discussed above, library() has a completely different meaning, and the opposite command is

detach(package:package-name)

which removes the package from the search path.

To make matters even more confusing, the argument to install.packages() is the “package-name” in quotation marks; the argument to library() is the package-name with or without quotation marks; and the argument to detach() is the form of the package-name that appears as the output of search(), which is like package:package-name with or without quotation marks!

You can confirm that you have successfully loaded or removed the package by issuing

search()

which shows what is attached to your search path (Figure 2).

Figure 2. Output of search(), library(), and detach() commands.

The functions within the loaded packages are available for you to access and use in your own R code or program. The names of these functions can be found by issuing (Figure 3)

getNamespaceExports(“package-name”)

Figure 3. Output of getNamespaceExports() command.

I mentioned above that packages can be installed on your computer by download from the CRAN repository. If you develop your own package, then you may want to eventually submit it to CRAN. But before you submit it, you need to do two things:

First, you need to build a .tar.gz source package, which is the format that is required for uploading to CRAN. That can be accomplished by

setwd(p) # p is the pathname to your package

devtools::document(roclets = c('rd', 'collate', 'namespace', 'vignette'))

b<-devtools::build()

The resulting .tar.gz source package will be located in the same directory as that containing your package (Figure 4). The returned parameter b is the path name for the .tar.gz source package.

Figure 4. Location of .tar.gz source package

Second, in order to use or test the functions within the source package, you need to install the source package on your computer from your local directory (in contrast to installing it from CRAN). That can be accomplished by

install.packages(b,repos=NULL,type='source')

where b is the path name for the .tar.gz source package that had been returned by b<-devtools::build() in the previous example.

The several commands in the sequence to take package folders containing your raw R program file to a functional package attached to your search path are not too tedious to execute once or twice. But if you are developing a set of inter-related packages, and you need to fine tune them, the process can become quite repetitive, confusing, and tedious. To facilitate this, within the NoviceDeveloperResources package I have provided the function

x<-checkBuildInstallSourcePackage(dir,packs,packCheck,autoLibrary)

where dir is a character string containing the path name of the directory holding the package folders, packs is a character vector of the names of the packages, packCheck is a character vector of the names of the packages (within packs) to subject to check(), and autoLibrary is a Boolean discussed just below.

The parameter packCheck allows the user to speed up the development process by specifying a subset of packs to subject to the rather lengthy check(). Of course, when the final packages are to be processed, packCheck should include all of packs.

The return value x contains a character vector that can be viewed in the proper format by

cat(x)

The output is shown in Figure 5. These lines can be copied and pasted into the R Console to load the current version of the packages into the search path. This is offered as an alternative to inclusion in the checkBuildInstallSourcePackage() function, as it is not permitted to automate code that can alter the user’s search path.

Figure 5. Output of cat(x)

There is a workaround to the safer (albeit more tredious) cat(x) procedure. If the Boolean parameter autoLibrary is set to TRUE, then we can bypass cat(x) and automate the detach() and library() procedures, by generating those commands using the eval(parse()) mechanism. This essentially tricks R Studio into not recognizing that we are indirectly generating the forbidden library() call.

If you are running checkBuildInstallSourcePackage() because you modified a certain package, then packs should include the name of that package as well as any other packages which import() that package. Otherwise those other packages may remain linked to the obsoleted version of that package. Furthermore, the names of these packages in the input list packs must be in the correct order so that the upper level packages import() the new version of the leaf node packages, rather than simply once again import() the obsolete version. This could be figured out manually, but the process is tedious and error-prone.

My related CRAN package NoviceDeveloperResources2 contains an integrated program sortedInputForCheckBuildInstallSourcePackageDriver() to invoke checkBuildInstallSourcePackage() with the package names in the correct order within packs, as well as to check for conflicts, as discussed in the immediately following section.

CONFLICT RESOLUTION

When you are developing the functions for your package, you may work back and forth between the R Console and R Studio. This may not be the best practice, but it has certain advantages. For instance, if you are debugging one of your functions, it is rather tedious to edit a change within R Studio, and then process the entire package just to try out the effect of the edit. It may be faster to copy the edited version of just the one function, and paste it into the R Console. After a while, you can lose track of which variant version is which – there may be one version that is in the global environment, and another variant version that is associated with the package. Unfortunately, the scoping mechanism may invoke the version that you did not intend, and it can be confusing as to why your edits did not seem to take effect.

To help resolve this type of conflict, I have provided two functions conflictOfInterest() and conflictOfInterestRestricted(packs) in the NoviceDeveloperResources package. The second version restricts the output of the first version to those packages specified in packs. This makes the output a little more focused for a human reader.

As shown in Figure 6, there is a conflict for my function mapfile(). While fine tuning this function, I inadvertently generated a version that is in the cardUtils package as well as a version that I had unwisely pasted into the global environment of the R Console.

Figure 6. Partial result of invoking conflictOfInterest().