It seems that even the origin of least squares is debateable:
https://blog.bookstellyouwhy.com/carl-friedrich-gauss-and-the-method-of-least-squares
"That Gauss was the first to define the method of least squares was contested
in his day. Adrien-Marie Legendre first published a version of
Hi all
Some MACs users are experiencing problems using TOPAS/TOPAS-Academic on a
MAC emulating windows. If you are using a successfully using TOPAS on a MAC
then can you please send me a private e-mail with the details of your
emulator; ie. is it Parallels Desktop, VMware Fusion, VirtualBox or
Hi Tony
>My I ask is this re-bined data from the measurement software considered as
"raw data" or "treated data"?
I'm not sure what is meant by treated data. Almost all neutron data and
synchrotron data with area detectors are "treated data".
If the detector has a slit width in the equa
Hi All
Just letting everyone know that TOPAS-Academic Version 7 is now available.
See http://www.topas-academic.net/ where New7.PDF and the
Technical_Reference.PDF can be downloaded.
The Bruker-AXS version won't be far behind.
Cheers
Alan
+++
Hi Kurt
TOPAS models absorption edges well. Page 158 of the Technical Reference at
http://www.topas-academic.net/Technical_Reference.pdf shows the result.
The macro in question is modifies the emission profile which is how I think
it should be modelled:
macro Absorption_Edge_Correction
Yes Frank, the macro is working with V5 of TOPAS-Academic; TOPAS should be the
same.
Cheers
Alan
-Original Message-
From: Frank Girgsdies
Sent: Monday, September 4, 2023 7:09 PM
To: alancoe...@bigpond.com
Cc: rietveld_l@ill.fr
Subject: Re: [EXT] Re: [External] Re: Step-like basline
degrees and less however reduces the problem consdierably for the FCJ
approach.
cheers
alan
-Original Message-
From: Larry Finger [mailto:[EMAIL PROTECTED]
Sent: Wednesday, 31 May 2006 7:25 AM
To: rietveld_l@ill.fr
AlanCoelho wrote:
> I would like to conclude that to be critical of a met
Great to hear form you Alexander
The mailing list is not really a lions den but you would
be forgiven for thinking so.
Ok Zuev, you have mistook my meaning in your point 4.1
below. It is not supposed to be “Self-explanatory”. The unreasonable conditions
I gave for when the convolution
a
Title: Message
The saga
continues
It has been
brought to my attention that the fit.xy data I provided in a previous e-mail has
misfits in the tails as seen in the following (blue is ray tracing, red is
convolution):
These misfits are due to how the ray tracing program
calculate
Miguel
I have seen low angle peaks that are void or have very little axial
divergence asymmetry. As an example, the low angle peak of Brucite in a
multiphase pattern often exhibits far less asymmetry that surrounding peaks
from different phases. This I am pretty sure is due to the preferred
orient
Pam, as the author of the INP format it was not my intention to make your
life difficult.
Maybe I am wrong but is it the case that we are now supposed to write into
CIF more than just primary/raw data. This to me is not what was originally
meant for CIF; non-primary data such as logical statement
Hi Sajeev
In XFIT the values of the observed data points in the xdd file needs to be
all greater than 1. Simply copy the xdd file into a spread sheet and set
values less than 1 to 1.
alan
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
Sent: Wednesday, 11 October 200
://members.optusnet.com.au/~alancoelho
All the bestAlan Coelho
Hi Bill and others
Why cant this question of zero counts be answered in a simple and practical
manner. I hope to read Devinder Sivia's excellent book one day but for the
time being it would be useful if the statistical heavy weights were to
advise on what weighting is appropriate without everyone
lihood!
All the
best,
Bill
-Original
Message-From: AlanCoelho [mailto:[EMAIL PROTECTED]Sent: 13 October 2006
22:30To: rietveld_l@ill.frSubject: RE: About zero counts
etc.
Hi Bill and
others
Why cant this
question of zero counts be answered in a simple and practical
manner. I hope to
Hi Doug
You can add new setting in the file SGCOM5.CPP where entries are in the form
of computer adapted symbols by Uri Shmueli, Acta Cryst. (1984). A40,
559-567.
I am probably wrong but my guess for F12/d1 is
FMCI1A000P2D003
where I used the a+b face-diagonal rotation matrix of 2D, c
Representing data in Q space is fine for viewing etc... but the conversion
from 2Th to Q needs a little thought. If unequal Q steps is not a problem
then a straight conversion is ok. However if someone is going to use that Q
data for further analysis then it is important to use the original data
Simon Billinge wrote:
>We can resolve the problem by setting 2pi=1!
What school did you go to; thanks for the info.
This issue of plotting data is one of those's non-issues drummed up by
groups familar with one format but not in another; I would suggest that
everyone should be familar with both
Whether a program has a button to display data as a function of 1/d or a
button to take the square toor of intensities is trivial to the point of not
being talked about much less setting up web sites to get opinions.
The only point worth talking about is how a conversion from 2Th to 1/d is
done i
one. There are obviously favorable points and cons. Why
we cannot discuss it. Seems like for the Rietveld users is not so
trivial.
Oh, and no one is setting up web sites just to show
opinions.may be these were already there...
Cheers,
Luca
On Feb 21, 2007, at 8:11 PM,
Leandro
Not sure what the purpose of your refinement is but if it's quantification
then your results would probably be in error to a large extent.
The references given by Alan Hewat and Lubo Smrcok is probably a good
starting point.
Data quality and model errors typically mean that atomic positi
Clay people
I think the single crystal analysis of clays is interesting. I have not read
the literature but in determining the intensities is overlap of the dots
considered as I would have expected the dots to be very much smeared (5 to
10 degrees 2Th in my experience). If yes the fitting in two d
Lubo
SVD as you mentioned does avoid numerical problems as does other methods
such as the conjugate gradient method. SVD minimizes on the residuals |A x -
b| after solving the matrix equation A x = b.
I would like to point out however that errors obtained from the covariance
matrix are an approxi
Not sure what to make of all this Jon
I am to believe that scientists prefer to mull over source code rather than
pseudo code and mathematical descriptions. Anyone that knows just a little
about software development would know that source code is the last thing
that one wants to see. How many has
Vincent
In the original message of Michael Love (forwarded by Jon Wright) it clearly
states:
> Although there are still some small problems, I think that this is a
> big step forward, and certainly an interesting read, if you are
> interested in FOSS and science.
What does "still some problems
olicy update regarding source code]
AlanCoelho wrote:
> Not sure what to make of all this Jon
Don't shoot the messenger, I was surprised enough by it to forward it to
the list. I guess they imply if you want to keep all implementation
details secret you should be patenting instead
Vincent wrote:
"It is a step forward for F/OSS as it acknowledges that open-source code
allows to spread a new method better than a closed source. As opposed to,
filing a patent - since patents were originally developed to ensure that new
methods be available to all."
You are right in that open s
Brian
>I personally feel that open source software is usually in the best
interests of scientific
>methods development.
This is a matter of opinion but even if you are right then no one has the
right to deny non-publically funded bodies the right to practice science.
Science or knowledge
Alan
A very good take on the situation and I totally agree that Nature Materials
should provide free access to all of its articles; otherwise it preaches one
thing and practices another.
One of the articles at nature.com concerns Public Library of Science
http://www.nature.com/nature/debates/e-ac
Vincent
>For another software with many important contributors it would indeed be
>impossible. But then the software would not have existed in the first place
>with a non-free license, so.
This discussion is getting nowhere; I politely disagree and see no solution;
never is it right to developm
One last reassuring word to the users of TOPAS - if I may
No open source algorithm under any license comes close to equalling those as
implemented in TOPAS and its academic counterpart. This status quo shall
remain.
In the event that commercial entities are locked out of journals then in the
case
Hi Maria
Automatic Divergence Slits (ADS) illuminate different parts of the post
monochromator as a function of 2Th. I am guessing but I think that the
crystals are good enough not to change the intensity too much; this is my
experience with Y2O23 in any case.
At around 70 to 80 degrees 2Th howe
Hi Xiujun
Topas implements a normalized symmetrized sperical harmonics function, see
Jarvine
J. Appl. Cryst. (1993). 26, 525-531
http://scripts.iucr.org/cgi-bin/paper?S0021889893001219
The expansion is simply a series that is a function hkl values.
The series is normalized s
HI all
Looking at the Pair Distribution Function and refinement I come away with
the following:
Fitting in real space (directly to G(r)) should be equivalent to fitting to
reciprocal space except for a difference in the cost function. Is this
difference beneficial in any way. In other words
Thanks all for the PDF explanations
I think I'm beginning to understand. To summarise what we know:
- PDF for powder data is a Patterson function (as Alan Hewat stated) in one
dimension that plots the histogram of atom separation
- It will show quite nicely the short range order and then possibl
Hi Frank
I'm not 100% sure what you have been doing but I think the copying and
pasting to get LVol values for particular sets of hkls can be maybe done in
a more simple manner as shown below. If it's not clear then contact me off
the list.
prm lor_h00 300 min .3
prm lor_0k0 300 min .3
p
Hi Ross
There's no way of outputting a selection of hkls; it's all or none.
You can however omit hkls at the start of the refinement; ie.
omit_hkls = And(H, K, Mod(L, 2));
omit_hkls = H > 10;
etc...
You can use this in an indirect manner to first refine using all hkls an
Lee Wrote
>I have some ToF data from GEM ISIS as both a .gss and a .asc file. I have
>managed to import and refine this using GSAS but am having some
>difficulties importing into TOPAS. Does anyone have some advice please on
>maybe file exchange or getting this file into the correct format to be
>
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