1 .TH g_filter 1 "Thu 16 Oct 2008"
3 g_filter - frequency filters trajectories, useful for making smooth movies
10 .BI "-n" " index.ndx "
11 .BI "-ol" " lowpass.xtc "
12 .BI "-oh" " highpass.xtc "
24 g_filter performs frequency filtering on a trajectory.
25 The filter shape is cos(pi t/A) + 1 from -A to +A, where A is given
28 times the time step in the input trajectory.
29 This filter reduces fluctuations with period A by 85%, with period
30 2*A by 50% and with period 3*A by 17% for low-pass filtering.
31 Both a low-pass and high-pass filtered trajectory can be written.
36 writes a low-pass filtered trajectory.
37 A frame is written every
40 This ratio of filter length and output interval ensures a good
41 suppression of aliasing of high-frequency motion, which is useful for
42 making smooth movies. Also averages of properties which are linear
43 in the coordinates are preserved, since all input frames are weighted
44 equally in the output.
45 When all frames are needed, use the
52 writes a high-pass filtered trajectory.
53 The high-pass filtered coordinates are added to the coordinates
54 from the structure file. When using high-pass filtering use
57 or make sure you use a trajectory which has been fitted on
58 the coordinates in the structure file.
62 Trajectory: xtc trr trj gro g96 pdb cpt
66 Structure+mass(db): tpr tpb tpa gro g96 pdb
72 .BI "-ol" " lowpass.xtc"
74 Trajectory: xtc trr trj gro g96 pdb
76 .BI "-oh" " highpass.xtc"
78 Trajectory: xtc trr trj gro g96 pdb
82 Print help info and quit
84 .BI "-nice" " int" " 19"
87 .BI "-b" " time" " 0 "
88 First frame (ps) to read from trajectory
90 .BI "-e" " time" " 0 "
91 Last frame (ps) to read from trajectory
93 .BI "-dt" " time" " 0 "
94 Only use frame when t MOD dt = first time (ps)
97 View output xvg, xpm, eps and pdb files
99 .BI "-nf" " int" " 10"
100 Sets the filter length as well as the output interval for low-pass filtering
103 Write all low-pass filtered frames
105 .BI "-[no]nojump" "yes "
106 Remove jumps of atoms across the box
109 Fit all frames to a reference structure