Typically, plot.bayesm.hcoef will be invoked by a call to the generic plot function as in
plot(object) where object is of class bayesm.hcoef. All of the bayesm hierarchical routines
return draws of hierarchical coefficients in this class (see example below). One can also simply invoke
plot.bayesm.hcoef on any valid 3-dim array as in plot.bayesm.hcoef(betadraws)
plot.bayesm.hcoef is also exported for use as a standard function, as in
plot.bayesm.hcoef(array).