[gmx-users] coordinates of the mass center

[yren at home.ipe.ac.cn]

Dear GMX users:
   I want to calculate the coordinates of the  mass center of a protein in
 pdb format.  Does anyone know which function in GMX can realize this?
As far as I know,  g_dist offers the distance between mass center of
two groups without  provision mass center of the groups.
   Thank you guys in adcance.