This package can be installed as a regular R package, that is,
   install.packages(cppcor)

if the GTK+ library is not already installed on your system,
installation may fail.

On Windows, the user must set the GTK_PATH environment variable to the
location of the root directory of the GTK+ library (ie \c:\opt\gtk). Try
downloading the GTK+ bundle from:

http://ftp.gnome.org/pub/gnome/binaries/win64/gtk+/2.22/gtk+-bundle_2.22.1-20101229_win64.zip
or
http://ftp.gnome.org/pub/gnome/binaries/win32/gtk+/2.22/gtk+-bundle_2.22.1-20101227_win32.zip

Then add the path to its “bin” subfolder (e.g., c:\opt\gtk\bin) to your system PATH environment
variable.

Another alternative for installing the GTK + library
in R software itself is install and load
the gWidgetsRGtk2 package in advance on R:
   install.packages("gWidgetsRGtk2")
   library(gWidgetsRGtk2)

A new window dialog window will appear, asking if you want to install “GTK+”.
Select “Install GTK” and then “OK”. This way the GTK + library will be installed automatically.

To install PCCor on Linux, you have to first install the following
required dependencies. On Debian and Ubuntu-based systems,
to install those packages open a terminal and type:
  sudo apt-get install r-cran-cairodevice r-cran-rgtk2 libcairo2-dev libatk1.0-dev libpango1.0-dev libgtk2.0-dev libglib2.0-dev libcurl4-openssl-dev


This README file was written based on the INSTALL and README files of RGTk2 and
MODIStsp packages, respectively. Of which the latter was very well detailed.
The links to these files follow:

RGTk2, INSTALL: https://cran.r-project.org/web/packages/RGtk2/INSTALL
MODISstp, README: https://cran.r-project.org/web/packages/MODIStsp/readme/README.html