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       g_angle  -  calculates  distributions  and  correlations for angles and

       VERSION 4.0.1


       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 -nice int -b time -e time  -dt  time  -[no]w  -[no]xvgr
       -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


       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 indexfile 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 andsin of
       selected dihedral angles which subsequently can be used as input for  a
       PCA analysis using  g_covar.


       -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


        Print help 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)

        View output xvg, xpm, eps and pdb files

        Add  specific  codes  (legends  etc.)  in the output xvg files for the
       xmgrace program

       -type enum angle
        Type  of  angle  to   analyse:    angle,    dihedral,    improper   or

        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

        Print dihedral angles modulo 360 degrees

        Use Chandler correlation function (N[trans] = 1, N[gauche] = 0) rather
       than  cosine  correlation function. Trans is defined as phi  -60 || phi

        Average the correlation functions for the individual angles/dihedrals

       -acflen int -1
        Length of the ACF, default is half the number of frames

        Normalize ACF

       -P enum 0
        Order of Legendre polynomial for ACF (0 indicates none):  0,  1,  2 or

       -fitfn enum none
        Fit  function:   none,   exp,   aexp,   exp_exp,  vac,  exp5,  exp7 or

       -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 till the end


       - Counting transitions only works for dihedrals with multiplicity 3



       More      information     about     GROMACS     is     available     at

                                Thu 16 Oct 2008                     g_angle(1)