ipop,
for allele iall of locus ilocPlotFreq(path.mcmc,ipop,iloc,iall,printit=FALSE,path)MCMC
was launched with option filter.null.alleles=TRUE, an extra
fictive allele standing for putative null alleles is created. It
estimated frequency can be also plotted. If there is say, 5 alleles
at a locus, the estimated frequency of null alleles can be seen
invoking PlotFreq with iall=6.