minor corrections on .Rd

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/erpr@49 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
correction on butterfly.R

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/erpr@50 edb9625f-4e0d-4859-8d74-9fd3b1da38cb