[Ifeffit] Artemis fit results question

[Bruce Ravel]

On Tuesday 31 August 2004 10:06 am, Kelly, Shelly D. wrote:
> -Most often negative values is a strong indication that something in the
> model is not quite right.  Be sure to look at your data and fits showing
> the individual contribution from each path in the real or imaginary part
> of the FT.

I wanted to expand on this little part of Shelly's excellent response
to Timm's question.

The ability to quickly and easily plot the data, the fit, and each
individual path is one of Artemis' main strengths.  You should
definately do as Shelly suggests and compare to the data each path
that you consider including in the fit.  This comparison should be
made as the real and/or imaginary parts of chi(R) as well as the
magnitude.  And this comparison should be done both before and after a
fit.  Sometimes problems in a fitting model that are unclear when
plotting the fit and looking at the log file become quite transparent
when looking at the real/imaginary parts of each contributing path.

To plot things, they need to be selected.  In the language of Artemis
"selected" means "highlighted in orange".  You can select multiple
entries in the Data and Paths List by holding down the control key
while clicking the left mouse button on items in the list.  Other
mouse event combinations that are useful for doing extended selection
are shift-click and click-drag.  Paths also must be "included" in the
fit to be plotted.  The included ones are the ones written in black
text.  The excluded ones are the ones written in brown text.

HTH,
B


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 Bruce Ravel  ----------------------------------- ravel at phys.washington.edu
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