[gmx-users] gyration radius

[Ran Friedman]

Sorry for insisting, but I still don't get it:

If I only take a single frame, e.g.:

@ s0 legend "Rg"
@ s1 legend "RgX"
@ s2 legend "RgY"
@ s3 legend "RgZ"
         1     1.76618     1.21448     1.50536     1.58042

I get Rg= sqrt ((Rx^2 + Ry^2 + Rz^2) * 0.5)

Thanks,
Ran.

David van der Spoel wrote:

>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.
>>
>>    
>>

-- 
------------------------------------------------------
Ran Friedman
Laser Laboratory for Fast Reactions in Biology
Department of Biochemistry
Faculty of Life Sciences
Tel-Aviv University
Tel. +972-3-6409824
Fax. +972-3-6409875
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