Requirements

You need gnuplot module for ConTeXt http://ctan.org/pkg/context-gnuplot and a recent version of ConTeXt. If you want to call gnuplot on-the-fly, you also need write18 enabled. In most TeX distributions this can be set with shell_escape=t in texmf.cnf.

See http://wiki.contextgarden.net/Gnuplot for details about this terminal and for more exhaustive help & examples.