forced directed placement graph?

["Park, Richard" <Richard.Park@joslin.harvard.edu>]

Does anyone have, or know in which library we could find, an S-Plus algorithm for "force-directed placement" graph drawing (taking a set of correlation or other similarity metrics and positionning them on a 2-D plane, optimizing the X,Y position of each object in relation to their relative correlations.

Thanks, 

Richard Park