SetLegendWorld — Position the legend on the image (world coordinates)
$plot->SetLegendWorld($x,$y)
SetLegendWorld lets you position the legend on the
image, using world coordinates, rather than letting PHPlot position it for you.
(World coordinates are the coordinate space of your data points.)
$x, $yWorld coordinates of the upper left corner of the legend box. The units and origin are the same as the data you are plotting.
Through PHPlot-5.0rc3, it was required that the data array, axis types, and any other setting which affects the scale of the data be set up before this function is used. Starting at PHPlot-5.0.4 this is no longer required, as the coordinates you supply are not scaled until the plot is drawn.
See also SetLegendPixels.