the fill down function & its required sorting function [for the latter enter the dataframe and what taxon group (i.e., MRTs, genera, families, etc) you want out for output] -- fill down function gives warnings (i think these can be ignored for now) *********NEW VERSION (09-apr-08): warnings are fixed (thanks to brody and kabir!), Additions: (1) a check that the required columns (family, genus, Taxon) are present; (2) a check that does not allow the required columns to be filled down********NEWER VERSION (11-apr-08): now all the warnings are fixed and the siftData function works for specific subsets of the columns********NEWEST VERSION(21-apr-08): now the subspp without spp entries works