Man page - gmx-gangle(1)

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Manual

GMX-GANGLE

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
SEE ALSO
COPYRIGHT

NAME

gmx-gangle - Calculate angles

SYNOPSIS

gmx gangle [ -f [<.xtc/.trr/...>] ] [ -s [<.tpr/.gro/...>] ] [ -n [<.ndx>] ]
[ -oav [<.xvg>] ] [ -oall [<.xvg>] ] [ -oh [<.xvg>] ]
[ -b <time> ] [ -e <time> ] [ -dt <time> ] [ -tu <enum> ]
[ -fgroup <selection> ] [ -xvg <enum> ] [ -[no]rmpbc ]
[ -[no]pbc ] [ -sf <file> ] [ -selrpos <enum> ]
[ -seltype <enum> ] [ -g1 <enum> ] [ -g2 <enum> ] [ -binw <real> ]
[ -group1 <selection> ] [ -group2 <selection> ]

DESCRIPTION

gmx gangle computes different types of angles between vectors. It supports both vectors defined by two positions and normals of planes defined by three positions. The z axis or the local normal of a sphere can also be used as one of the vectors. There are also convenience options 'angle' and 'dihedral' for calculating bond angles and dihedrals defined by three/four positions.

The type of the angle is specified with -g1 and -g2 . If -g1 is angle or dihedral , -g2 should not be specified. In this case, -group1 should specify one or more selections, and each should contain triplets or quartets of positions that define the angles to be calculated.

If -g1 is vector or plane , -group1 should specify selections that contain either pairs ( vector ) or triplets ( plane ) of positions. For vectors, the positions set the endpoints of the vector, and for planes, the three positions are used to calculate the normal of the plane. In both cases, -g2 specifies the other vector to use (see below).

With -g2 vector or -g2 plane , -group2 should specify another set of vectors. -group1 and -group2 should specify the same number of selections. It is also allowed to only have a single selection for one of the options, in which case the same selection is used with each selection in the other group. Similarly, for each selection in -group1 , the corresponding selection in -group2 should specify the same number of vectors or a single vector. In the latter case, the angle is calculated between that single vector and each vector from the other selection.

With -g2 sphnorm , each selection in -group2 should specify a single position that is the center of the sphere. The second vector is calculated as the vector from the center to the midpoint of the positions specified by -group1 .

With -g2 z , -group2 is not necessary, and angles between the first vectors and the positive Z axis are calculated.

With -g2 t0 , -group2 is not necessary, and angles are calculated from the vectors as they are in the first frame.

There are three options for output: -oav writes an xvg file with the time and the average angle for each frame. -oall writes all the individual angles. -oh writes a histogram of the angles. The bin width can be set with -binw . For -oav and -oh , separate average/histogram is computed for each selection in -group1 .

OPTIONS

Options to specify input files:
-f [<.xtc/.trr/...>] (traj.xtc) (Optional)

Input trajectory or single configuration: xtc trr cpt gro g96 pdb tng

-s [<.tpr/.gro/...>] (topol.tpr) (Optional)

Input structure: tpr gro g96 pdb brk ent

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

Extra index groups

Options to specify output files:
-oav [<.xvg>] (angaver.xvg) (Optional)

Average angles as a function of time

-oall [<.xvg>] (angles.xvg) (Optional)

All angles as a function of time

-oh [<.xvg>] (anghist.xvg) (Optional)

Histogram of the angles

Other options:
-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 if t MOD dt == first time (ps)

-tu <enum> (ps)

Unit for time values: fs, ps, ns, us, ms, s

-fgroup <selection>

Atoms stored in the trajectory file (if not set, assume first N atoms)

-xvg <enum> (xmgrace)

Plot formatting: xmgrace, xmgr, none

-[no]rmpbc (yes)

Make molecules whole for each frame

-[no]pbc (yes)

Use periodic boundary conditions for distance calculation

-sf <file>

Provide selections from files

-selrpos <enum> (atom)

Selection reference positions: atom, res_com, res_cog, mol_com, mol_cog, whole_res_com, whole_res_cog, whole_mol_com, whole_mol_cog, part_res_com, part_res_cog, part_mol_com, part_mol_cog, dyn_res_com, dyn_res_cog, dyn_mol_com, dyn_mol_cog

-seltype <enum> (atom)

Default selection output positions: atom, res_com, res_cog, mol_com, mol_cog, whole_res_com, whole_res_cog, whole_mol_com, whole_mol_cog, part_res_com, part_res_cog, part_mol_com, part_mol_cog, dyn_res_com, dyn_res_cog, dyn_mol_com, dyn_mol_cog

-g1 <enum> (angle)

Type of analysis/first vector group: angle, dihedral, vector, plane

-g2 <enum> (none)

Type of second vector group: none, vector, plane, t0, z, sphnorm

-binw <real> (1)

Binwidth for -oh in degrees

-group1 <selection>

First analysis/vector selection

-group2 <selection>

Second analysis/vector selection

SEE ALSO

gmx(1)

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COPYRIGHT

2025, GROMACS development team