g_angle(1)

NAME
g_angle - calculates distributions and correlations for angles and dihedrals VERSION 4.5.4-dev-20110404-bc5695c

SYNOPSIS
g_angle -f traj.xtc -n angle.ndx -od angdist.xvg -ov angaver.xvg -of dihfrac.xvg -ot dihtrans.xvg -oh trhisto.xvg -oc dihcorr.xvg -or traj.trr -[no]h -[no]version -nice int -b time -e time -dt time -[no]w -xvg enum -type enum -[no]all -binwidth real -[no]periodic -[no]chandler -[no]avercorr -acflen int -[no]normalize -P enum -fitfn enum -ncskip int -beginfit real -endfit real

DESCRIPTION
g_angle computes the angle distribution for a number of angles or dihedrals. This way you can check whether your simulation is correct. With option -ov you can plot the average angle of a group of angles as a function of time. With the -all option the first graph is the average, the rest are the individual angles. With the -of option, g_angle also calculates the fraction of trans dihedrals (only for dihedrals) as function of time, but this is probably only fun for a selected few. With option -oc a dihedral correlation function is calculated. It should be noted that the index file should contain atom-triples for angles or atom-quadruplets for dihedrals. If this is not the case, the program will crash. With option -or a trajectory file is dumped containing cos and sin of selected dihedral angles which subsequently can be used as input for a PCA analysis using g_covar.

FILES
-f traj.xtc Input
 Trajectory: xtc trr trj gro g96 pdb cpt -n angle.ndx Input
 Index file -od angdist.xvg Output
 xvgr/xmgr file -ov angaver.xvg Output, Opt.
 xvgr/xmgr file -of dihfrac.xvg Output, Opt.
 xvgr/xmgr file -ot dihtrans.xvg Output, Opt.
 xvgr/xmgr file -oh trhisto.xvg Output, Opt.
 xvgr/xmgr file -oc dihcorr.xvg Output, Opt.
 xvgr/xmgr file -or traj.trr Output, Opt.
 Trajectory in portable xdr format

OTHER OPTIONS
-[no]hno
 Print help info and quit -[no]versionno
 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) -[no]wno
 View output .xvg, .xpm, .eps and .pdb files -xvg enum xmgrace
 xvg plot formatting: xmgrace, xmgr or none -type enum angle
 Type of angle to analyse: angle, dihedral, improper or ryckaert-bellemans -[no]allno
 Plot all angles separately in the averages file, in the order of appearance in the index file. -binwidth real 1
 binwidth (degrees) for calculating the distribution -[no]periodicyes
 Print dihedral angles modulo 360 degrees -[no]chandlerno
 Use Chandler correlation function (N[trans] = 1, N[gauche] = 0) rather than cosine correlation function. Trans is defined as phi -60 or phi 60. -[no]avercorrno
 Average the correlation functions for the individual angles/dihedrals -acflen int -1
 Length of the ACF, default is half the number of frames -[no]normalizeyes
 Normalize ACF -P enum 0
 Order of Legendre polynomial for ACF (0 indicates none): 0, 1, 2 or 3 -fitfn enum none
 Fit function: none, exp, aexp, exp_exp, vac, exp5, exp7, exp9 or erffit -ncskip int 0
 Skip N points in the output file of correlation functions -beginfit real 0
 Time where to begin the exponential fit of the correlation function -endfit real -1
 Time where to end the exponential fit of the correlation function, -1 is until the end

KNOWN PROBLEMS
- Counting transitions only works for dihedrals with multiplicity 3

SEE ALSO
gromacs(7) More information about GROMACS is available at <http://www.gromacs.org/>.