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)