GDXRRW is an interface between General Algebraic Modeling System (GAMS) and R. It includes functions to transfer data between GDX and R and a function to call gams from within R.

The R devtools package allows packages that are hosted on GitHub to be installed directly from there. This is a convenient way to install GDXRRW.

The devtools package is installed by running the following command in R.

install.packages("devtools")

devtools can then be loaded

library(devtools)

Installation from GitHub will install a package and all of its prerequisites (in this case the reshape2 package):

install_github("GAMS-dev/gdxrrw/gdxrrw")

To install a specific version of GDXRRW, the following command can be used.

install_github("GAMS-dev/gdxrrw/[email protected]")

After you install GDXRRW you may want to verify that the installation is functioning correctly. The GDXRRW package is not loaded by default, so before the package is available you must load it. This is easily done with the library(gdxrrw) command. Once the package is loaded, you can get help on the package as a whole (help(gdxrrw)) or the functions or data elements in the package (e.g. help(igdx)).

For GDXRRW to work it must load shared libraries from the GAMS system directory. One common problem is a failure to find the GAMS system directory and these shared libraries. The igdx command can be used to show what GAMS system directory GDXRRW has found (igdx()) and to point GDXRRW to a particular GAMS system directory if so desired (igdx(“/usr/local/gams/24.4.1”)). Depending on your system setup, environment variables, and how you start R, GDXRRW may not need any help finding the GAMS system directory, but the igdx command allows this binding to be queried and customized if desired.

The R sessionInfo() command tells you the version number of packages you have loaded, including gdxrrw.

The help pages for the other GDXRRW functions include examples that you can run to quickly verify your system is working.

If you are seeing GDXRRW for the first time you should look at the examples and tests that come with GDXRRW. For example, each of the functions wgdx, rgdx, igdx, and gams comes with integrated help and examples that can be accessed in the usual way within the R environment, e.g.: help(rgdx). In addition, more complete tests and more substantive examples are included in the gdxrrw package. For more recent package versions (0.6.0 and following), package tests are collected in the tests directory. Earlier versions put the tests in extdata. The sample commands below assume a recent version and sufficient access permission in the package install directory. If you lack such permission copy the files before using them. Some helpful R commands for testing are:

• setwd (paste0(path.package('gdxrrw'),'/tests'))
• execute the tAll.R script (source(“tAll.R”) to run the tests

Some examples are collected in the extdata directory:

• setwd (paste0(path.package('gdxrrw'),'/extdata'))
• In subdir TSP, execute the egTSP.R script to export data for a traveling salesman problem to GAMS, solve it, and return the solution to R for plotting
• In subdir LS, run the egLeastSquares.gms model from GAMS - this calls R as part of the GAMS run to do the data fitting and return the results

R provides multiple ways to customize the environment at startup, e.g. to start with the GDXRRW package loaded. One way is to use the .Rprofile script that is executed from the HOME directory when R starts up.

• For a description of how R starts up: help(Startup)
• To find your home directory, especially useful on Windows: Sys.glob(“~”)
• To load non-default libraries like GDXRRW on Linux startup, use a .Rprofile with this line:

    .First <- function() { library(gdxrrw) ; igdx("/home/sdirkse/gams/24.4.1")}

• On 64-bit Windows you can run 64- and 32-bit R. The .Rprofile handles the initialization easily:

    .First <- function() {
      library(gdxrrw)
      a <- R.Version()$arch
      if (a == "x86_64")  igdx("/gams_64/24.4.1")
      else                igdx("/gams_32/24.4.1")
    }

• To get system information, try Sys.getenv:
  • Sys.getenv(“R_LIBS_USER”) helps to find user-installed packages
  • Sys.getenv(“R_USER”) helps to locate the .Rprofile file, especially on Windows
• To get version information: R.Version

Here we have some helpful commands useful for building/testing the gdxrrw package if you are not using devtools(). Note that building binary or source packages are not necessary to simply build gdxrrw for your own use, and additional R packages (with their own requirements on installed software like tex, etc.) are required to build these binary or source packages.

We tend to build gdxrrw for 3 platforms, described here as an FYI and *not as a list of requirements. Our Linux build machine is currently Fedora Workstation 32, while our macOS machine is currently running Mohave. Both use typical GCC compilers. Our Windows builder is Windows 10. To build R or R packages from source on Windows it is typical (perhaps even required) to use the RTools packaging of GCC available here.

To INSTALL or build or test, it works well to NOT have library(gdxrrw) set in .Rprofile but to have the environment variable

R_GAMS_SYSDIR=/path/to/GAMS/sysdir

set and inherited by the R process.

N.B.: assume $rrw is the dir containing the package tree. This is also the top level of the git repo, or the directory containing the README.md file. We assume that you first make this the current directory:

cd $rrw

To install or remove/uninstall:

R CMD INSTALL gdxrrw
R CMD REMOVE gdxrrw

If the settings in your .Rprofile are getting in the way, you can direct R to not use .Rprofile, for example:

R --no-init-file CMD INSTALL gdxrrw

To make a platform-dependent binary distribution, do:

R CMD INSTALL gdxrrw --build

• To make a source distribution gdxrrw_X.Y.Z.tar.gz, do:

R CMD build gdxrrw

It is good practice to check this source distro:

R CMD check gdxrrw_X.Y.Z.tar.gz

We would love to get feedback on GDXRRW. Please direct your questions, comments, and suggestions to [email protected].