[gmx-users] how to create a index file for angle calculation

[SHAHEE ISLAM]

hi,
if i want to calculate angle between two group,then the group will be
in same file or in different file.because when i am using this command
gmx gangle -f md-0-1-300k-pbc.xtc -n index.ndx -dt 2000 -oall angle.xvg
 putting the two group (1 and 2 both) in same idex file , i am getting
the values for group1 and group2 separately.but i want to calculate
the angle between the two groups. both two groups contains three
residue.
thanking you
shahee