[Ifeffit] N independent variables

[Jesús Eduardo Vega Castillo]

Thank you once again Matt,

I am sorry for sending just a portion of the log file. I thought that way
it would be easier to look for  the details. Won't happen again.

Jesús






2016-05-23 16:31 GMT-03:00 Matt Newville <newville en cars.uchicago.edu>:

> Jesus,
>
>
> On Mon, May 23, 2016 at 2:07 PM, Jesús Eduardo Vega Castillo <
> jevecas en gmail.com> wrote:
>
>> Dear list,
>>
>> I made an EXAFS analysis in Artemis (in Demeter 0.9.22) using all the
>> available variables. This is a fragment of the .log file I got:
>>
>> Independent points          : 17.7666016
>> Number of variables         : 17
>> Chi-square                  : 265.0947132
>> Reduced chi-square          : 345.8050781
>>
>> R-factor                    : 0.0026486
>>
>> Number of data sets         : 1
>> : k-range               = 2.942 - 11.043
>> : dk                    = 1
>> : k-window              = hanning
>> : k-weight              = 1,2,3
>> : R-range               = 1.115 - 3.5
>> : dR                    = 0.0
>> : R-window              = hanning
>> : fitting space         = r
>> : background function   = yes
>> : phase correction      = no
>> : background removal    = E0: 20002.215, Rbkg: 1.0, range:
>> [2.25:17.4039986832903], clamps: 0/24, kw: 2
>> : epsilon_k by k-weight = 3.189e-004
>> : epsilon_r by k-weight = 2.339e-001
>> : R-factor by k-weight  = 1 -> 0.00220,  2 -> 0.00224,  3 -> 0.00392
>>
>> The problem is that when I use the Nyquist criterion
>>
>> Nind=2*deltak*deltar/pi + 1
>>
>> for calculating the number of independent points the value I got is much
>> lower and close to 13.
>>
>> I was not aware of this discrepancy and it caused a reviewer to think I
>> made up the fit!
>>
>>
> Sending the entire log file is always recommended.  Otherwise, you are
> selectively editing what you are telling us, and expecting us to guess what
> you haven't told us.  Sending the project file is often a good choice.
>
> Fortunately, you included an important clue.  You have "background
> function = yes", which means the fit will actually extend down to R=0,
> using your  Rmin as Rbkg in calculating how many variables are used for the
> spline.  With that included, the fit does contain approximately 18
> independent parameters, about 5 of which will be used for the background
> subtraction.
>
> --Matt
>
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