getRangeCartesian(
    P;
    xmin,
    xmax,
    ymin,
    ymax,
    extend,
    digits,
    force
)

Get the cartesian range over which the factor graph variables span.

Notes:

• Optional regexFilter can be used to subselect, according to label, which variable IDs to use.

DevNotes

• TODO, allow tags as filter too.