A rectangle is a list of 4 numbers; the first two elements are the x and y coordinates of lower left corner of the rectangle. The other two elements are the width and height of the rectangle.
Pushes a rectangle for the whole encapsulated page onto the PostScript stack. This pushed rectangle is an implicit argument to
partition-pageorsetup-plot.
Pops the rectangle currently on top of the stack and pushes xparts * yparts sub-rectangles onto the stack in decreasing y and increasing x order. If you are drawing just one graph, then you don't need
partition-page.
The rectangle where data points should be plotted. plotrect is set by
setup-plot.