[Ifeffit] Consistency criterion

Juan Antonio Maciá Agulló Juan.Macia at ua.es
Thu Sep 28 10:09:30 CDT 2006


Hi Scott,

Thanks a lot, you are a good fortune-teller. I have low-Z scatterers (oxygen)
and high-Z scatteres (Pt).

Best regards,
JA


Scott Calvin ha escrito:

> Hi Juan,
>
> They're consistent. The higher r-factor on the kwt-1 data might be a
> clue about how reliable part of your data range is...since it's the
> kwt-1 that's higher, it may be that the low end of the k-range is not
> being fit very well (look at the k-space and q-space fits to help
> confirm this). That could be just because of glitchy data, iffy
> background subtraction, or that your model doesn't do as well with
> low-Z scatterers like oxygen as it does with the higher-Z
> contributions (the low-Z scatterers have most of their contributions
> at low k). Aside from looking at the k- and q-space fits, I'd try
> increasing kmin and see if that improves the fit. If it does, you
> might want to do it on the kwt-3 fit too, because that would suggest
> you're not fitting that low-k data very well, and the problem is just
> less emphasized with kwt-3. Of course it would be even better to find
> the source of the problem and address it.
>
> Having said that, I should emphasize that these are non-linear fits.
> Sometimes it's hard to come up with a simple explanation for why one
> fit is closer than another.
>
> Nevertheless, your fits are consistent. They're not equally
> "good"...but that's a different statement. In your situation, I would
> be comfortable publishing the kwt-3 fit and saying that other kwts
> gave consistent results. I would be more comfortable if I could
> figure out what was troubling the kwt-1 fit, though...especially if I
> had a mix of scatterers with substantially different atomic number
> (like transition metals with oxygens).
>
> --Scott Calvin
> Sarah Lawrence College
>
> At 08:03 AM 9/28/2006, you wrote:
>
> >Hi all,
> >
> >Scott answered my question about consistency but now I have a new doubt.
> >I have two fits (one in k1 and other in k3 weights) with fitted
> >parameters that have
> >uncertainty ranges overlaped, then... in principle, they are consitent,
> >right?
> >But the fit in k1 weight have a R-factor too high (0.06) and therefore
> >is not a good fit. So I do not know if I can say that they are
> >consistent even so.
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Juan.Macia.vcf
Type: text/x-vcard
Size: 286 bytes
Desc: Tarjeta para Juan Antonio Maciá Agulló
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20060928/2b5d3a5e/attachment.vcf>


More information about the Ifeffit mailing list