[Ifeffit] Use of restraint

Maureen Le Bars le_bars at cerege.fr
Wed Jun 22 09:05:36 CDT 2016


Hello,

I have a couple of questions about data analysis on artemis

I used a restraint for my fits. I've read some documentation about it 
and found Matt Newville's talk 
(https://pubweb.bnl.gov/~frenkel/BNLworkshop2001/newville.pdf). It is 
reported that a restraint adds a "V" term to the chi-square (slides 
number 16 and 17).

According to this formula, what is the number that artemis gives for the 
"restrain" parameter at the end of the fit? How should we consider this 
number in the evaluation of the fit ?

I also don't really know very much about the scaling factor to apply in 
the formula : scale*penalty(X,a,b). I've read that the square root of 
chi-squareseems to be a good size from some of Bruce Ravel's answers in 
ifeffit mailing list. How does the scaling factor control the restraint 
? What is its relationship with the chi-square ?

Thank you in advance for your help,

Maureen

/PhD student at CIRAD - ADEME//
//CEREGE - Europôle de l'Arbois//
//BP 80//
//13545 Aix en Provence Cedex 4
France
+33 4 42 97 15 48/

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