xenial (1) gmx-trjconv.1.gz

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NAME

       gmx-trjconv - Convert and manipulates trajectory files

SYNOPSIS

          gmx trjconv [-f [<.xtc/.trr/...>]] [-s [<.tpr/.gro/...>]] [-n [<.ndx>]]
                      [-fr [<.ndx>]] [-sub [<.ndx>]] [-drop [<.xvg>]]
                      [-o [<.xtc/.trr/...>]] [-b <time>] [-e <time>]
                      [-tu <enum>] [-[no]w] [-xvg <enum>] [-skip <int>]
                      [-dt <time>] [-[no]round] [-dump <time>] [-t0 <time>]
                      [-timestep <time>] [-pbc <enum>] [-ur <enum>]
                      [-[no]center] [-boxcenter <enum>] [-box <vector>]
                      [-trans <vector>] [-shift <vector>] [-fit <enum>]
                      [-ndec <int>] [-[no]vel] [-[no]force] [-trunc <time>]
                      [-exec <string>] [-split <time>] [-[no]sep]
                      [-nzero <int>] [-dropunder <real>] [-dropover <real>]
                      [-[no]conect]

DESCRIPTION

       gmx trjconv can convert trajectory files in many ways:

       • from one format to another

       • select a subset of atoms

       • change the periodicity representation

       • keep multimeric molecules together

       • center atoms in the box

       • fit atoms to reference structure

       • reduce the number of frames

       • change the timestamps of the frames (-t0 and -timestep)

       • cut  the  trajectory  in  small  subtrajectories according to information in an index file. This allows
         subsequent analysis of the subtrajectories that  could,  for  example,  be  the  result  of  a  cluster
         analysis. Use option -sub.  This assumes that the entries in the index file are frame numbers and dumps
         each group in the index file to a separate trajectory file.

       • select frames within a certain range of a quantity given in an .xvg file.

       gmx trjcat is better suited for concatenating multiple trajectory files.

       The following formats are supported for input and output: .xtc, .trr, .gro,  .g96  and  .pdb.   The  file
       formats  are  detected  from the file extension.  The precision of .xtc and .gro output is taken from the
       input file for .xtc, .gro and .pdb, and from the -ndec option for other input formats. The  precision  is
       always  taken  from  -ndec, when this option is set.  All other formats have fixed precision. .trr output
       can be single or double precision, depending on the precision of  the  gmx  trjconv  binary.   Note  that
       velocities are only supported in .trr, .gro and .g96 files.

       Option  -sep  can  be  used  to  write every frame to a separate .gro, .g96 or .pdb file. By default, all
       frames all written to one file.  .pdb files with all  frames  concatenated  can  be  viewed  with  rasmol
       -nmrpdb.

       It  is  possible  to select part of your trajectory and write it out to a new trajectory file in order to
       save disk space, e.g. for leaving out the water from a trajectory of a protein in water.  ALWAYS put  the
       original trajectory on tape!  We recommend to use the portable .xtc format for your analysis to save disk
       space and to have portable files.

       There are two options for fitting the trajectory to a reference either for essential  dynamics  analysis,
       etc.   The  first option is just plain fitting to a reference structure in the structure file. The second
       option is a progressive fit in which the first timeframe is fitted to  the  reference  structure  in  the
       structure file to obtain and each subsequent timeframe is fitted to the previously fitted structure. This
       way a continuous trajectory is generated, which might not be the case when using the regular fit  method,
       e.g. when your protein undergoes large conformational transitions.

       Option -pbc sets the type of periodic boundary condition treatment:

          • mol  puts  the  center of mass of molecules in the box, and requires a run input file to be supplied
            with -s.

          • res puts the center of mass of residues in the box.

          • atom puts all the atoms in the box.

          • nojump checks if atoms jump across the box and then puts them back. This has  the  effect  that  all
            molecules  will  remain whole (provided they were whole in the initial conformation). Note that this
            ensures a continuous trajectory but molecules may diffuse out of the box. The starting configuration
            for  this  procedure is taken from the structure file, if one is supplied, otherwise it is the first
            frame.

          • cluster clusters all the atoms in the selected index such that they are all closest to the center of
            mass  of the cluster, which is iteratively updated. Note that this will only give meaningful results
            if you in fact have a cluster. Luckily that can be checked afterwards  using  a  trajectory  viewer.
            Note also that if your molecules are broken this will not work either.

            The  separate  option  -clustercenter  can be used to specify an approximate center for the cluster.
            This is useful e.g. if you have two big vesicles, and you want to maintain their relative positions.

          • whole only makes broken molecules whole.

       Option -ur sets the unit cell representation for options mol, res and atom of -pbc.   All  three  options
       give  different  results  for  triclinic  boxes and identical results for rectangular boxes.  rect is the
       ordinary brick shape.  tric is the triclinic unit cell.  compact puts all atoms at the  closest  distance
       from  the  center  of  the  box.  This  can be useful for visualizing e.g. truncated octahedra or rhombic
       dodecahedra. The center for options tric and compact is tric (see below), unless the option -boxcenter is
       set differently.

       Option  -center  centers  the system in the box. The user can select the group which is used to determine
       the geometrical center.  Option -boxcenter sets the location of the center of the box  for  options  -pbc
       and  -center.  The  center  options  are: tric: half of the sum of the box vectors, rect: half of the box
       diagonal, zero: zero.  Use option -pbc mol in addition to -center when you want all molecules in the  box
       after the centering.

       Option  -box  sets  the  size  of  the new box. This option only works for leading dimensions and is thus
       generally only useful for rectangular boxes.  If you want to modify only some  of  the  dimensions,  e.g.
       when  reading  from a trajectory, you can use -1 for those dimensions that should stay the same It is not
       always possible to use combinations of -pbc, -fit, -ur and -center to do exactly what  you  want  in  one
       call to gmx trjconv. Consider using multiple calls, and check out the GROMACS website for suggestions.

       With -dt, it is possible to reduce the number of frames in the output. This option relies on the accuracy
       of the times in your input trajectory, so if these are inaccurate use the -timestep option to modify  the
       time  (this  can be done simultaneously). For making smooth movies, the program gmx filter can reduce the
       number of frames while using low-pass frequency  filtering,  this  reduces  aliasing  of  high  frequency
       motions.

       Using  -trunc gmx trjconv can truncate .trr in place, i.e.  without copying the file. This is useful when
       a run has crashed during disk I/O  (i.e.  full  disk),  or  when  two  contiguous  trajectories  must  be
       concatenated without having double frames.

       Option  -dump  can be used to extract a frame at or near one specific time from your trajectory, but only
       works reliably if the time interval between frames is uniform.

       Option -drop reads an .xvg file with times and values.  When options -dropunder and/or -dropover are set,
       frames with a value below and above the value of the respective options will not be written.

OPTIONS

       Options to specify input files:

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

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

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

       -fr [<.ndx>] (frames.ndx) (Optional)
              Index file

       -sub [<.ndx>] (cluster.ndx) (Optional)
              Index file

       -drop [<.xvg>] (drop.xvg) (Optional)
              xvgr/xmgr file

       Options to specify output files:

       -o [<.xtc/.trr/...>] (trajout.xtc)
              Trajectory: xtc trr gro g96 pdb tng

       Other options:

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

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

       -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

       -skip <int> (1)
              Only write every nr-th frame

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

       -[no]round (no)
              Round measurements to nearest picosecond

       -dump <time> (-1)
              Dump frame nearest specified time (ps)

       -t0 <time> (0)
              Starting time (ps) (default: don't change)

       -timestep <time> (0)
              Change time step between input frames (ps)

       -pbc <enum> (none)
              PBC treatment (see help text for full description): none, mol, res, atom, nojump, cluster, whole

       -ur <enum> (rect)
              Unit-cell representation: rect, tric, compact

       -[no]center (no)
              Center atoms in box

       -boxcenter <enum> (tric)
              Center for -pbc and -center: tric, rect, zero

       -box <vector> (0 0 0)
              Size for new cubic box (default: read from input)

       -trans <vector> (0 0 0)
              All coordinates will be translated by trans. This can advantageously be combined with -pbc mol -ur
              compact.

       -shift <vector> (0 0 0)
              All coordinates will be shifted by framenr*shift

       -fit <enum> (none)
              Fit molecule to ref structure in the structure file: none, rot+trans, rotxy+transxy,  translation,
              transxy, progressive

       -ndec <int> (3)
              Precision for .xtc and .gro writing in number of decimal places

       -[no]vel (yes)
              Read and write velocities if possible

       -[no]force (no)
              Read and write forces if possible

       -trunc <time> (-1)
              Truncate input trajectory file after this time (ps)

       -exec <string>
              Execute command for every output frame with the frame number as argument

       -split <time> (0)
              Start writing new file when t MOD split = first time (ps)

       -[no]sep (no)
              Write each frame to a separate .gro, .g96 or .pdb file

       -nzero <int> (0)
              If the -sep flag is set, use these many digits for the file numbers and prepend zeros as needed

       -dropunder <real> (0)
              Drop all frames below this value

       -dropover <real> (0)
              Drop all frames above this value

       -[no]conect (no)
              Add  conect  records  when writing .pdb files. Useful for visualization of non-standard molecules,
              e.g. coarse grained ones

SEE ALSO

       gmx(1)

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

       2015, GROMACS development team