Dear Teemu, Thank you for your explanation. Now I understand why the first selection gives more residues as it's simply a superset of the second selection. I just realized to accomplish what I initially want, i.e., to obtain the residue index list of LIPID whose center of mass is within 1.0 nm of the surface of protein, I just need
group "LIPID" and res_com within 1.0 of group "PROTEIN" and g_select -sf selection.dat -f traj.trr -s traj.tpr -n system.ndx -oi index.dat -seltype res_com -selrpos atom Again, I am a bit confused by that it seems the sole function of -seltype res_com is outputting residue index instead of atom index. If I use -seltype atom instead, g_select will return all the corresponding atoms in the residues selected by the selection just above. What frustrates me most is I can't find a flag to be used in selection.dat to let g_select output residue index, not atom index. Best Regards, Bin -- Gromacs Users mailing list * Please search the archive at http://www.gromacs.org/Support/Mailing_Lists/GMX-Users_List before posting! * Can't post? Read http://www.gromacs.org/Support/Mailing_Lists * For (un)subscribe requests visit https://maillist.sys.kth.se/mailman/listinfo/gromacs.org_gmx-users or send a mail to gmx-users-requ...@gromacs.org.
