gmx-filter - Frequency filter trajectories, useful for making smooth movies

       2025, GROMACS development team

2025.0                                            Feb 10, 2025                                     GMX-FILTER(1)

gmxfilter 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.

       gmx-filter - Frequency filter trajectories, useful for making smooth movies

       Options to specify input files:

       -f[<.xtc/.trr/...>](traj.xtc)
              Trajectory: xtctrrcptgrog96pdbtng-s[<.tpr/.gro/...>](topol.tpr)(Optional)
              Structure+mass(db): tprgrog96pdb brk ent

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

       Options to specify output files:

       -ol[<.xtc/.trr/...>](lowpass.xtc)(Optional)
              Trajectory: xtctrrgrog96pdbtng-oh[<.xtc/.trr/...>](highpass.xtc)(Optional)
              Trajectory: xtctrrgrog96pdbtng

       Other options:

       -b<time>(0)
              Time of first frame to read from trajectory (default unit ps)

       -e<time>(0)
              Time of last frame to read from trajectory (default unit ps)

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

       -[no]w(no)
              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]all(no)
              Write all low-pass filtered frames

       -[no]nojump(yes)
              Remove jumps of atoms across the box

       -[no]fit(no)
              Fit all frames to a reference structure

gmx(1)

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

          gmx filter [-f[<.xtc/.trr/...>]] [-s[<.tpr/.gro/...>]] [-n[<.ndx>]]
                     [-ol[<.xtc/.trr/...>]] [-oh[<.xtc/.trr/...>]]
                     [-b<time>] [-e<time>] [-dt<time>] [-[no]w] [-nf<int>]
                     [-[no]all] [-[no]nojump] [-[no]fit]