[gmx-users] least-squares fit

[David]

On Fri, 2002-10-18 at 17:11, Nguyen Hoang Phuong wrote:
> 
> Dear All,
> 
> I have one question concerning to the least-squares fit in GROMACS:
> 
> suppose I have two structures obtained at the time t=0 and t=T with set of
> the coordinates of atoms {r_n} and {R_n}, respectively. I have done as the
> following: I fit the structure {R_n} to {r_n} and calculate the
> quantities: delta_r = R'_n - {r_n} where {R'_n} are the coordinates
> obtained after fitting. 
> 
> Next, I fit the structure {r_n} to {R_n} and calculate the 
> quantities: delta_r' = r'_n - {R_n} where {r'_n} are the coordinates 
> obtained after fitting.
> 
> The result is that delta_r differs delta_r'. According to the
> least-squares fit method, the two results must be the same. Does anyone
> know what the reason is? Thanks a lot in advance.

Are you sure? I tried it using g_confrms -f1 X.pdb -f2 Y.pdb and the
other way around. I get exactly the same results (6 digits). How large
is the discrepancy in your case?
> 
> Regards,
> 
> Phuong
> 
> 
> 
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-- 
Groeten, David.
________________________________________________________________________
Dr. David van der Spoel, 	Biomedical center, Dept. of Biochemistry
Husargatan 3, Box 576,  	75123 Uppsala, Sweden
phone:	46 18 471 4205		fax: 46 18 511 755
spoel at xray.bmc.uu.se	spoel at gromacs.org   http://zorn.bmc.uu.se/~spoel
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