Bob,
for the negative points in case of a background subtraction I do a
little trick. If the resulting data is negative I do the square root
of the absolute value and I multiply by -1 (I retain the sign). So it
plots in sqrt but remains negative.
Luca
On Feb 21, 2007, at 10:14 PM, Von Dreele, Robert B. wrote:
Actually, I looked at Luca's little "show" & was sufficiently
interested
that GSAS will now plot sqrt(I) style plots. There is one "problem" -
the value of "I" can be negative particularly after a background
subtraction. These must be suppressed to zero for this plot to work -
thus there is a small risk of something getting hidden. Anyway -
the new
version will be out in a day or two (after I make sure there are no
bugs
introduced by this!)
R.B. Von Dreele
IPNS Division
Argonne National Laboratory
Argonne, IL 60439-4814
-----Original Message-----
From: Luca Lutterotti [mailto:[EMAIL PROTECTED]
Sent: Wednesday, February 21, 2007 2:59 PM
To: rietveld_l@ill.fr
Subject: Re: Powder Diffraction In Q-Space
Alan,
if it is trivial to plot in the square root I presume it is already
available in Topas as well GSAS and Fullprof just to mention few. And
if it is so trivial and already available as a button options why no
one is using it. Why every time I look at a paper with a Rietveld
refinement I can only appreciate the big peaks and why the residuals
are so little meaningful at end? Every one can choose what he prefers
obviously, but why all (without exceptions) are using not exactly the
best way to just do a plot? Should not be trivial?
Conversion from 2theta - d -1/d is trivial in MY OPINION. This is
really a problem of the programmer not of the users (in a Rietveld
list). Constant step or variable step? Why it should influence the
conversion except for the speed of the conversion. I am using fast
fourier transform in my program for computing peak profiles directly
from distribution of crystallites and microstrain; I don't assume any
constant step, but seems like I can do it.
And this step or FT has really nothing to do with the original post
of Klaus-Dieter who was focusing on just asking people if we can try
to get used to a common way to plot data different from the
conventional 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, AlanCoelho wrote:
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 in regards to takeing the fourier transform of a powder pattern.
alan
-----Original Message-----
From: Joerg Bergmann [mailto:[EMAIL PROTECTED]
Sent: Thursday, 22 February 2007 4:30 AM
To: rietveld_l@ill.fr
Subject: Re: Powder Diffraction In Q-Space
It's a principle of software design not to presume any kind of
equidistant data. Unfortunately, file formats for non-equidistant
data
are seldom. So I could not implement any in BGMN, until now. But, in
principle, there is no restriction.
Regards
Joerg Bergmann
