rad-class for methods to create a rank-abundance
data frame; radpred to get a rad-class object of
predicted abundances from a theoretical distribution;
fitsad-class , fitsadC-class and
fitrad-class objects, from which you can also get an
object of class rad; qqrad for quantile-quantile
plots from a rad-class object, and pprad for
percentile-percentile plots.