[R] Drawing paths through a grid

[Rex C. Eastbourne]

I would like to draw a set of points that are equally spaced in a 2-D
grid. Then I would like to draw lines that illustrate different
directed paths through subsets of points. Imagine that the points
correspond to booths in a conference center, and I want to show the
various paths people took to visit the booths (using color to
highlight different types of paths). An example path might be: [(1,1),
(1,3), (3, 3)].

Note: I would like to also make the size of the points in the grid
variable (they correspond to the sizes of the booth).

Can anyone suggest a way to do this in R? (Or to suggest another
software package.)

Thanks,
Rex