[gmx-users] gyration radius

[David van der Spoel]

On Wed, 2005-07-20 at 10:58 -0400, Ran Friedman wrote:
> Hello,
> 
> I'm trying to understand the relation between the total radius of 
> gyration and its components. Searching to the mailing list, I found     
> that Rg = sqrt (Rx^2 + Ry^2 + Rz^2), see 
> http://www.gromacs.org/pipermail/gmx-users/2003-October/007376.html
> 
> But what I got was:
> 
> set     average              stddev
> SS1   1.744821e+00   2.028432e-02   (Rg)
> SS2   1.195420e+00   1.366429e-02   (Rx)
> SS3   1.485673e+00   2.606876e-02   (Ry)
> SS4   1.565914e+00   2.048274e-02   (Rz)
> 
> which means:
> Rg = sqrt ((Rx^2 + Ry^2 + Rz^2) * 0.5)
> 
> What's wrong?
> 
You should do the averaging after summing up the components.


> Thanks,
> Ran.
> 
-- 
David.
________________________________________________________________________
David van der Spoel, PhD, Assoc. Prof., Molecular Biophysics group,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,          75124 Uppsala, Sweden
phone:  46 18 471 4205          fax: 46 18 511 755
spoel at xray.bmc.uu.se    spoel at gromacs.org   http://xray.bmc.uu.se/~spoel
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