REMARK: This R version (0.9), is a port of the S-plus version. You can only 
choose one (and only one) variable in «addreg.show», and the documentation 
file is writen for S-plus uses. Except this all, as far as I knows, it work as 
in the S-plus version. Planes for addreg version 1.1 includes the same 
support for R as for S-plus.