Re: Re: aniso scaling

[ravi@cmb2.saha.ernet.in (S.Ravichandran)]

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Hello..

	Continuing the argument on 'aniso' scaling..

>"Felix Vajdos" <vajdos@dna-mail4.gene.com> wrote:
>
>I don't have a good explanation for it, but my gut instinct tells
>me that it has to do with the fact that Xplor scales Fobs, not Fcalc.
>I can't really get my brain arond what may mathematically happening,...
>


	Well, if you look into the text books on crystallography, the
simple equation for R-factor calculation involves a 'scale factor' (k)
which is 'always' applied to Fcalc.           

like..   R-factor =  Sigma(hkl)(w(|Fobs| - k|Fcalc|)/Sigma(hkl)|Fobs|
                                           ^
                                           |-> scale factor 

Even, if you look into the XTALMACRO of the X-PLOR module..
you will find the following lines..

macro {scalef}
(

	.....
	....
   #f=fcalc;    {name of structure factor array -- scaling will be applied }

	....
	....
   #fref=fobs;  {name of reference structure factor array (f will be scaled to
fref}
	....

)


So, here, Fcalc is scaled to Fobs...

     If I am wrong in pointing out this.... I 'm sorry.

Sincerely,
Ravi.
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	 |                   S.Ravichandran                     |  
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