[Fwd: Re: GSAS data formats]

[Robert Von Dreele]

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I don't think this went to the mailing list

On Mar 16, 2009, at 7:44 AM, Robert Von Dreele wrote:

Hi,

Brian is correct in that the 'FXYE' format is "best" as it is the simplest to implement. It requires 3 columns of data in free format (either floating point or exponental forms are OK). 1st column is position (in centidegrees), 2nd is intensity (corrections can be applied if needed) & 3rd is esd (error propagation for corrections applied here). The STD format is no. counters & intensity. The intensities are all on same basis i.e. the average over the number of counters used to collect that point. GSAS calculates the esd (& weight) using the number of detectors. BTW - the GSAS Manual indicated that records need be 82 characters long. This is no longer true. Records can be shorter.

Best,
Bob Von Dreele
----- Original Message -----
From: "Brian H. Toby" <brian.t...@anl.gov>
Date: Monday, March 16, 2009 0:30 am
Subject: Re: GSAS data formats
To: matthew.row...@csiro.au
Cc: rietveld_l@ill.fr

I do not recommend using this format. Better choices are the ESD
 variant on this, where numbers are alternated intensity, esd,

intensity... (and there are a lot more digits for each number) or the

 FXYE format, which has angle, intensity, and optionally esd, one
 entry per line in free format.

 My recollection on this is that YO is the total number of counts, so

 the normalized Intensity = YO/n and the error on that is SQRT(YO)/n.

 The idea being that not all measurements are made with the same
 number of detectors.

 Brian

 On Mar 16, 2009, at 12:02 AM, matthew.row...@csiro.au wrote:

Hi all

I'm going over the GSAS data format (by reading the manual), trying

to figure out how it works, and I've come up with a couple of
questions:

1) In a STD data set, the manual says that NCTR is the number of
counters and YO is the n number of counts per counter.

So, for a single data point " 3  3452", is the total counts =3*3452?
What is the error? Sqrt(3*3452), 3*sqrt(3452) or sqrt(3452/3)?


2) What is the data format for type = "ALT"? The manual (http://
www.ccp14.ac.uk/ccp/ccp14/ftp-mirror/gsas/public/gsas/manual/
GSASManual.pdf) doesn't say...



Cheers

Matthew

________________
Matthew Rowles

CSIRO Minerals
Box 312
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AUSTRALIA 3169

Ph: +61 3 9545 8892
Fax: +61 3 9562 8919 (site)
Email: matthew.row...@csiro.au

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 Brian H. Toby, Ph.D.                            office: 630-252-5488
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Brian H. Toby, Ph.D.                            office: 630-252-5488
Senior Physicist/Materials Characterization Group Leader
Advanced Photon Source
9700 S. Cass Ave, Bldg. 433/D003             work cell: 630-327-8426
Argonne National Laboratory         secretary (Marija): 630-252-5453
Argonne, IL 60439-4856         e-mail: brian dot toby at anl dot gov
********************************************************************

"We will restore science to its rightful place, and wield technology's wonders... We will harness the sun and the winds and the soil to fuel our cars and run our factories... All this we can do. All this we will do."

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