Simpler syntax with suffix argument (and character arguments)

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/lava@1238 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
null argument added

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/lava@1239 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Default id variable from rownames

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/lava@1240 edb9625f-4e0d-4859-8d74-9fd3b1da38cb