# [gmx-users] The dihedral angles from 192 elements ??

Tsjerk Wassenaar tsjerkw at gmail.com
Thu Jul 3 07:10:39 CEST 2008

```Lin,

This is manual stuff...:

http://www.gromacs.org/documentation/reference/online/g_angle.html

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.

Which clearly (!) states that your first plot is a distribution of all
angles measured over time for each dihedral in your set (piled
together) and that your second plot calculates an average for your set
of dihedrals for each frame.

Tsjerk

On Thu, Jul 3, 2008 at 1:02 AM, Chih-Ying Lin <chihying2008 at gmail.com> wrote:
> Hi
> Four atoms form a set of diheral angles.
>
> When I do g_angle for the dihedral angle calculation, it shows
>
> Group     0 (Phi=180.0_2_70) has     4 elements
> Group     1 (Phi=180.0_2_6) has    16 elements
> Group     2 (Phi=180.0_2_40) has   192 elements
> Select a group:
>
> If I select Group 2, there is 192 elements (192=48*4), it means there
> are 48 sets of dihedal angles).
>
> the command
> g_angle -od angdist.xvg -ov angaver.xvg type diheral
>
> output 2 plots: angdist.xvg   and   angaver.xvg
>
> what does the two plots mean for the 48 sets of dihedral angles??
> Are the two plots average over the 48 sets of dihedral angles?
>
>
>
> Thanks  a  lot
> Lin
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--
Tsjerk A. Wassenaar, Ph.D.
Junior UD (post-doc)
Biomolecular NMR, Bijvoet Center
Utrecht University