Consult S's on-line help for more details on the functions described above. In particular, the pcmid function has several optional arguments and components in its result which, for the sake of brevity, have not been mentioned here; typing help(pcmid) will give you information on these.
For more information on S model formulæ, consult Becker, Chambers and Wilks, The New S Language, Section 2.2. Section 2.3.2 of the same book, and help(C) or help(contr.sum) will give you more information on the parameterisation of factors in S.
help(plot.variogram) gives information in arguments to plot specific to plotting variograms.