| ## g_traj Main Table of Contents | VERSION 4.6 Sat 19 Jan 2013

### Description

`g_traj` plots coordinates, velocities, forces and/or the box. With `-com` the coordinates, velocities and forces are calculated for the center of mass of each group. When `-mol` is set, the numbers in the index file are interpreted as molecule numbers and the same procedure as with `-com` is used for each molecule.

Option `-ot` plots the temperature of each group, provided velocities are present in the trajectory file. No corrections are made for constrained degrees of freedom! This implies `-com`.

Options `-ekt` and `-ekr` plot the translational and rotational kinetic energy of each group, provided velocities are present in the trajectory file. This implies `-com`.

Options `-cv` and `-cf` write the average velocities and average forces as temperature factors to a `.pdb` file with the average coordinates or the coordinates at `-ctime`. The temperature factors are scaled such that the maximum is 10. The scaling can be changed with the option `-scale`. To get the velocities or forces of one frame set both `-b` and `-e` to the time of desired frame. When averaging over frames you might need to use the `-nojump` option to obtain the correct average coordinates. If you select either of these option the average force and velocity for each atom are written to an `.xvg` file as well (specified with `-av` or `-af`).

Option `-vd` computes a velocity distribution, i.e. the norm of the vector is plotted. In addition in the same graph the kinetic energy distribution is given.

### Files

option | filename | type | description
--- | --- | --- | ---
`-f` | `traj.xtc` | Input | Trajectory: xtc trr trj gro g96 pdb cpt
`-s` | `topol.tpr` | Input | Structure+mass(db): tpr tpb tpa gro g96 pdb
`-n` | `index.ndx` | Input, Opt. | Index file
`-ox` | `coord.xvg` | Output, Opt. | xvgr/xmgr file
`-oxt` | `coord.xtc` | Output, Opt. | Trajectory: xtc trr trj gro g96 pdb cpt
`-ov` | `veloc.xvg` | Output, Opt. | xvgr/xmgr file
`-of` | `force.xvg` | Output, Opt. | xvgr/xmgr file
`-ob` | `box.xvg` | Output, Opt. | xvgr/xmgr file
`-ot` | `temp.xvg` | Output, Opt. | xvgr/xmgr file
`-ekt` | `ektrans.xvg` | Output, Opt. | xvgr/xmgr file
`-ekr` | `ekrot.xvg` | Output, Opt. | xvgr/xmgr file
`-vd` | `veldist.xvg` | Output, Opt. | xvgr/xmgr file
`-cv` | `veloc.pdb` | Output, Opt. | Protein data bank file
`-cf` | `force.pdb` | Output, Opt. | Protein data bank file
`-av` | `all_veloc.xvg` | Output, Opt. | xvgr/xmgr file
`-af` | `all_force.xvg` | Output, Opt. | xvgr/xmgr file

### Other options

option | type | default | description
--- | --- | --- | ---
`-[no]h` | bool | `no` | Print help info and quit
`-[no]version` | bool | `no` | 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)
`-tu` | enum | `ps` | Time unit: `fs`, `ps`, `ns`, `us`, `ms` or `s`
`-[no]w` | bool | `no` | View output `.xvg`, `.xpm`, `.eps` and `.pdb` files
`-xvg` | enum | `xmgrace` | xvg plot formatting: `xmgrace`, `xmgr` or `none`
`-[no]com` | bool | `no` | Plot data for the com of each group
`-[no]pbc` | bool | `yes` | Make molecules whole for COM
`-[no]mol` | bool | `no` | Index contains molecule numbers iso atom numbers
`-[no]nojump` | bool | `no` | Remove jumps of atoms across the box
`-[no]x` | bool | `yes` | Plot X-component
`-[no]y` | bool | `yes` | Plot Y-component
`-[no]z` | bool | `yes` | Plot Z-component
`-ng` | int | `1` | Number of groups to consider
`-[no]len` | bool | `no` | Plot vector length
`-[no]fp` | bool | `no` | Full precision output
`-bin` | real | `1` | Binwidth for velocity histogram (nm/ps)
`-ctime` | real | `-1` | Use frame at this time for x in `-cv` and `-cf` instead of the average x
`-scale` | real | `0` | Scale factor for `.pdb` output, 0 is autoscale

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