EXODUS
Note that the EXODUS module is a general XOP utility and has a help
page from XOP.
However, it has some additional functionality for XAFS, and these items
are activated when starting EXODUS from XAID.
In this help page, only the XAFS particularities are treated.
Module characteristics
- Goal: to load a SPEC file,
or multiple ASCII files, and selecting, viewing,
averaging, and perform operations with data from multiple scans.
- Input: A SPEC file, an
individual or multiple ASCII multicolumn files
- Output: The data contained
in EXODUS can be exported to other programs, including XAID applications, or exported to files
in several formats.
-
Tricks:
- Multiple selection:
for exploiting all the possibilities of EXODUS, it is essential to know
how to select multiple lines in the lists. Click on a line for a single
line selection. Then press Shift and click on another line on the same
window (while Shift
is pressed) for selecting a block of lines. For selecting multiple individual
lines use Control
instead of Shift.
Example of Use
- Start
EXODUS from the main XAID window

- Load
Data by either
- Import a SPEC file
The list of scans appears in the left window.
Copy from left (import) window to right (process) window the data
to be processed
- Import multiple ASCII files. For instance using:

and selecting trhe Gezeo*.*
files in the xaid/Examples
directory:

As a result, the different data files are loaded into EXODUS, which
shows multiple data lines:

- Select the first line, and Export: XAID/Mu2Chi. A new
XAID_MU2CHI window will appear. Enter the
needed conversion factor to go from keV to eV (and
"Enter")
:
. Then click
for getting the EXAFS signal:

Then, in the XAID_MU2CHI window, open File->Preferences...
and set:

Now, XAID_MU2CHI is
prepared to receive multiple data sets.
- Without quitting XAID_MU2CHI,
go to the EXODUS window and perform a multiple selection:

and Export:
XAID/Mu2Chi. You will see new lines appearing in the EXODUS
window, containing the EXAFS signals of the input lines, as calculated
by XAID_MU2CHI:

- Without deselecting them, Export:
XAID/ff. The Fourier
Transforms of the signals are calculated, and the outputs are sent to
new lines in the EXODUS window:

- The
selected data in EXODUS can be exported in several formats. For instance,
Export: XPLOT/SPEC Mesh will create a 3D mesh with the corresponding Spec
file (if wanted):

- The
Operations pulldown menu allows to average, interpolate
and make calculations with data. Some operations
are:
- Operations:do
on each set ->Interpolate This option builds interpolated or
resampled data sets from the selected ones. The interpolated/resampled
data sets will have the same abscissas array. The abscissas array can
be selected between different options: i) like the first data set, ii)
customized with constant step in Energy scale, and iii) customized
with constant step in k scale. The results can be added to the
list of data sets (right panel) or be injected in XPlot for visualizing
in 2D (multiple column format) or in 3D.
Two algorithms are available:
i) Interpolation: linear interpolation.
The y value for the new x value is calculated by linear interpolation
between the two closer neighbours. This option is recommended when the
number of points of the interpolated array is of the order or bigger than
the number of points of the original array.
ii) Resample: Some kind of smooth interpolation.
For each resampled point x[i] of xNew it calculates yNew
consisting in the average y values of all points (x,y) sitting
in the interval [x[i]-0.5*step1,x[i]+0.5*step2], with step1=x[i]-x[i-1]
and step2=x[i+1]-x[i]. In the case that step1 or step2 are undefined
(first and last points) we used step=[x[1]-x[0]] instead step1
or step2
- Operations:->Interpolate
and-> Average This option
averages the selected data sets. For that, if the abscissas are different,
it makes an interpolation (see before). The result is added to the list
in the right panel.
- Operations:->Interpolate and->Sum
This option sums the selected data sets. For that, if the abscissas are
different, it makes an interpolation (see before). The result is added
to the list in the right panel.
- Operations:->Interpolate and->Customized
This option allows you to program a customized operation. The result is
added to the list in the right panel.
- Operations:->Interpolate and->Fit
LinCom This option allows you to perform fit a given data set in
the list (target) as a linear combination of other data sets (components)
in the list. This option is useful whilst analyzing XANES spectra of compounds
or mixtures, and wanted to know the percent of its components. The data
sets to be used as target and components are identified by their indices
in the right panel list, starting from zero. If the list is long, you
may want to use the View:->Info
option to help in identifying the indices of the wanted data sets. The
fit is performed using the Levenberg-Marquardt [MINPACK-1] method as implemented
in the MPFit IDL routine. The result of the fit
is added to the right panel list.
- Operations-One each set-> XANES normalization
- Operations-Parameters
from blocks. This
option permits to extract a parameter from each selected data set. It
is useful to calculate parameters from multiple spectra versus the spectra
number: Examples:
- For calculating
the standard deviation of the spectra enter: out=(moment(y))[1]
- For calculating
the integral of the spectra enter: out=int_tabulated(x,y)