\documentclass{ppex} \nonstopmode \usepackage [all,web]{xy}\usepackage {ifthen} \pagestyle{empty} \setlength\textwidth{183.0pt} \begin{document} \ResetPreambleCommands \ReadyForTheFray \usepackage [all,web]{xy}\usepackage {ifthen} \[\renewcommand{\latticebody}{% \ifthenelse{\latticeA=1}{% \ifthenelse{\latticeB=1}{\drop{\dir{*}}}% {\drop{\dir{o}}}}% {\drop{\dir{x}}}} \begin{xy} *\xybox{0;<8mm,4mm>:<4mm,8mm>:: ,0,{\croplattice{-6}{6}{-6}{6}% {-3}{3}{-3.5}{3.5}}% }="S" ,{"S"+L \ar "S"+R*+!L{z_1}} ,{"S"+D \ar "S"+U*+!D{z_2}} \end{xy}\] \end{document}