Points (Number of points in real space) in GNOM

Interactive and automated data processing tools (PRIMUS, GNOM, AUTORG).
Scattering from simple bodies (BODIES), peak analysis (PEAK), data plotting (SASPLOT) etc.
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georg
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Points (Number of points in real space) in GNOM

#1 Post by georg » 2020.04.23 12:24

Dear All,
I wanted to ask about the Points windows (Number of points in real space) in GNOM. I don't understand the meaning, function, how it is calculated. The manual says "Number of points in real space, in which the distribution function will be specified (less than 72). Default number of NREAL is evaluated by GNOM in order to have reasonable ratio
(number-of-data-points)/(number-of-parameters-to-be-found).

And in Practical advices

GNOM is intended to be as user-friendly as possible, that is, it normally runs OK using the default answers. In particular, default value of the number of real space points is highly recommended to use.

When I try different ranges to see where I should cut at smax and also play with Dmax the Points decrease but never goes up again. Should I set at the
end to 256 again or 200 or? When looking for Dmax and range should I have the points at a specific value? Is the value written out in the GNOM.out?
Depending on the dataset the points number changes more or less when I cahnge range, Dmax, ... . Does the points tell also something about dataquality?

Many thanks, br Georg.

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AL
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Re: Number of points in real space in GNOM

#2 Post by AL » 2020.05.11 11:20

GNOM's number of points in real space cannot be higher than the number of input points in reciprocal space. And it cannot be more than 256. When you use GNOM from PRIMUSqt, the number of points might be automatically decreased when you decrease the input data range.
Please note, the GNOM manual is a bit outdated.

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