NAME

       g_filter - frequency filters trajectories, useful for making smooth movies

       VERSION 4.6.5

SYNOPSIS

       g_filter -f traj.xtc -s topol.tpr -n index.ndx -ol lowpass.xtc -oh highpass.xtc -[no]h -[no]version -nice
       int -b time -e time -dt time -[no]w -nf int -[no]all -[no]nojump -[no]fit

DESCRIPTION

        g_filter performs frequency filtering on a trajectory.  The filter shape is cos(pi t/A) + 1 from  -A  to
       +A, where A is given by the option  -nf times the time step in the input trajectory.  This filter reduces
       fluctuations with period A by 85%, with period 2*A by 50%  and  with  period  3*A  by  17%  for  low-pass
       filtering.  Both a low-pass and high-pass filtered trajectory can be written.

       Option   -ol  writes  a  low-pass filtered trajectory.  A frame is written every  -nf input frames.  This
       ratio of filter length and output interval ensures a  good  suppression  of  aliasing  of  high-frequency
       motion,  which  is  useful  for making smooth movies. Also averages of properties which are linear in the
       coordinates are preserved, since all input frames are weighted equally in the output.   When  all  frames
       are needed, use the  -all option.

       Option   -oh writes a high-pass filtered trajectory.  The high-pass filtered coordinates are added to the
       coordinates from the structure file. When using high-pass filtering use  -fit or  make  sure  you  use  a
       trajectory that has been fitted on the coordinates in the structure file.

FILES

       -f traj.xtc Input
        Trajectory: xtc trr trj gro g96 pdb cpt

       -s topol.tpr Input, Opt.
        Structure+mass(db): tpr tpb tpa gro g96 pdb

       -n index.ndx Input, Opt.
        Index file

       -ol lowpass.xtc Output, Opt.
        Trajectory: xtc trr trj gro g96 pdb

       -oh highpass.xtc Output, Opt.
        Trajectory: xtc trr trj gro g96 pdb

OTHER OPTIONS

       -[no]hno
        Print help info and quit

       -[no]versionno
        Print version info and quit

       -nice int 19
        Set the nicelevel

       -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)

       -[no]wno
        View output  .xvg,  .xpm,  .eps and  .pdb files

       -nf int 10
        Sets the filter length as well as the output interval for low-pass filtering

       -[no]allno
        Write all low-pass filtered frames

       -[no]nojumpyes
        Remove jumps of atoms across the box

       -[no]fitno
        Fit all frames to a reference structure

SEE ALSO

       gromacs(7)

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

                                                 Mon 2 Dec 2013                                      g_filter(1)