[NTG-context] gnuplot in ConTeXt

Dear all, I have installed gnuplot and others(aqua term, x11). I tested the minimal sample file in ConTeXt Wiki. In the wiki page, there is a command like \startGNUPLOTgraphics{sin} plot sin(x) \stopGNUPLOTgraphics but there is an error message like l.6 \startGNUPLOTgraphics {sin} ? x If I changed \startGNUPLOTgraphics{sin} to \startGNUPLOTgraphic{sin}, then the error is disappeared but the output showed only texts but not graph. Only a grey box is appeared. Would you please show me an example in detail? Thank you for reading. Dalyoung