I do not know the answer to this question.
Skyline external tools are .zip files. Inside of the .zip file is a folder called "tool-inf" which tells Skyline how to install the external tool.
In the QuaSAR zip file, it says that it needs R version 3.0.1.
Also, there is a file in there called "tool-inf/InstallPackages.r" which Skyline runs after installing R version 3.0.1.
When I try to install the QuaSAR external tool in Skyline, I see errors such as:
Warning: unable to access index for repository http://cran.us.r-project.org/bin/windows/contrib/3.0
package 'bitops' is available as a source package but not as a binary
package 'bitops' is not available (for R version 3.0.1)
This error comes from executing the line in "Install.Packages.r":
install.packages("bitops" , repos='http://cran.us.r-project.org')
It looks like the problem might be that the packages are no longer available from the r-project website because the version of R that QuaSAR wants to use is too old. I do not know what should be done about that if that is the case.
Maybe someone who is more of an expert on installing R could answer this. Maybe there would be some way to point to a different repository.