[Ifeffit] Fwd: problems with setting parameters in new Artemis (Demeter 0.9.16)
Chris Patridge
patridge at buffalo.edu
Fri Feb 28 07:04:08 CST 2014
Hi,
The easiest constraint would be a mathematical expression such as "a + b = 1". Do you have an experimental value for so2 as found for something chemically similar such as a standard at that edge? Then replace so2 expression for each path as "value found * a" and "value found * b". This should give a relative percentage for each path contribution.
Hope that is clear,
Chris
********************************************
Dr. Christopher Patridge
Assistant Professor of Chemistry
Math and Natural Science Dept
BFAC 009
D'Youville College
320 Porter Ave., Buffalo, NY 14150
716-829-8096
Sent from my iPhone
> On Feb 28, 2014, at 7:52 AM, Cristina Alonso Escobar <criales at itq.upv.es> wrote:
>
> Dear All,
>
> I am trying to fit the first FT shell in Artemis with a mixture of two different compounds (octahedral and tetrahedral models). I would like to quantify the ratio between this two compounds in my sample so I decided to multiply So2 by a parameter called "a" in one model and by "(1-a)" in the other.
>
> I would like to know:
>
> 1.- How can I restrain "a" ? I tried to manually add a restraint, but I do not know how to make an interval restraint...( 0<a<1)
>
> 2.- If you select "restrain" and after in the math expression "build restrain from ..."
> What is the meaning of scale by?
> Why the program duplicate the restrain (i.e restrain- a and restrain- res_a - 1* penalty (a, 0, 1)?
> I think I am not doing well because the value of my parameter "a" is suspiciously always 0.
>
>
>
> Thank you in advance,
>
>
>
> *** *** *** *** *** *** *** *** ***
>
> Cristina Alonso-Escobar. PhD student
>
> Instituto de Tecnología Química (UPV-CSIC)
> Avda. de los Naranjos s/n
> 46022 Valencia (Spain)
>
> http://itq.upv-csic.es
>
> Tfno: +34 96 387 7800
> Fax: +34 96 387 9444
>
> ----- Terminar mensaje reenviado -----
>
>
> *** *** *** *** *** *** *** *** ***
>
> Cristina Alonso-Escobar. PhD student
>
> Instituto de Tecnología Química (UPV-CSIC)
> Avda. de los Naranjos s/n
> 46022 Valencia (Spain)
>
> http://itq.upv-csic.es
>
> Tfno: +34 96 387 7800
> Fax: +34 96 387 9444
>
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