Show the packages specified by the user and compare these to the installed packages on the user's system. Display packages not installed.
showPacks(packs=c("PBSmodelling","PBSmapping","PBSddesolve",
"rgl","deSolve","akima","deldir","sp","maptools","KernSmooth"))string vector of package names that are compared to installed packages.
Invisibly returns a list of Apacks (all packages installed on user's system),
Ipacks (packages in packs that are installed), and
Mpacks (packages that are missing).