NAME

       gmx-principal - Calculate principal axes of inertia for a group of atoms

SYNOPSIS

          gmx principal [-f [<.xtc/.trr/...>]] [-s [<.tpr/.gro/...>]]
                       [-n [<.ndx>]] [-a1 [<.xvg>]] [-a2 [<.xvg>]]
                       [-a3 [<.xvg>]] [-om [<.xvg>]] [-b <time>] [-e <time>]
                       [-dt <time>] [-tu <enum>] [-[no]w] [-xvg <enum>]
                       [-[no]foo]

DESCRIPTION

       gmx  principal  calculates the three principal axes of inertia for a group of atoms. NOTE:
       Old versions of GROMACS wrote the output data in a strange transposed way. As  of  GROMACS
       5.0,  the  output  file  paxis1.dat  contains  the  x/y/z  components of the first (major)
       principal axis for each frame, and similarly for the middle and minor axes  in  paxis2.dat
       and paxis3.dat.

OPTIONS

       Options to specify input files:

       -f [<.xtc/.trr/...>] (traj.xtc)
              Trajectory: xtc trr cpt gro g96 pdb tng

       -s [<.tpr/.gro/...>] (topol.tpr)
              Structure+mass(db): tpr gro g96 pdb brk ent

       -n [<.ndx>] (index.ndx) (Optional)
              Index file

       Options to specify output files:

       -a1 [<.xvg>] (paxis1.xvg)
              xvgr/xmgr file

       -a2 [<.xvg>] (paxis2.xvg)
              xvgr/xmgr file

       -a3 [<.xvg>] (paxis3.xvg)
              xvgr/xmgr file

       -om [<.xvg>] (moi.xvg)
              xvgr/xmgr file

       Other options:

       -b <time> (0)
              First frame (ps) to read from trajectory

       -e <time> (0)
              Last frame (ps) to read from trajectory

       -dt <time> (0)
              Only use frame when t MOD dt = first time (ps)

       -tu <enum> (ps)
              Unit for time values: fs, ps, ns, us, ms, s

       -[no]w (no)
              View output .xvg, .xpm, .eps and .pdb files

       -xvg <enum>
              xvg plot formatting: xmgrace, xmgr, none

       -[no]foo (no)
              Dummy option to avoid empty array

SEE ALSO

       gmx(1)

       More information about GROMACS is available at <http://www.gromacs.org/>.

COPYRIGHT

       2015, GROMACS development team