Dear R-help users, i used R to costruct the Delaunay triangulation with delaunayn function: vertex=delaunayn(3d_coord, option="QJ") of geometry package. 3d_coord is a matrix that contain 3d coordinates (x,y,z) of 160 points in the 3d space. I understand that not all of this point are used by delaunay function to constract the polyedrons. So now i need to obtain the coordintate x,y,z only that are used by delaunay function to construct these poliedrons. Best regards Piero Ricchiuto Gruppo di Studio per la Proteomica e la Struttura delle Proteine Dipartimento di Scienze Farmacologiche Università degli Studi di Milano Via Giuseppe Balzaretti, 9 20133 - Milano tel.: +39-02-50318395, fax: +39-02-50318284 [[alternative HTML version deleted]]