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--- data:line_fitting_idl [2024/11/11 20:30]
Peter Young created
+++ data:line_fitting_idl [2024/11/12 18:02] (current)
Peter Young [IDL Software for Emission Line Fitting]
@@ Line 1: / Line 1: @@
-====== Emission line fitting using IDL software ======
+====== IDL Software for Emission Line Fitting ======
+===== Fitting a Gaussian at each spatial pixel in a raster =====
+Spectra at each spatial pixel in a raster can be fit with Gaussians using the eis\_auto\_fit IDL routine developed for the Hinode/EIS mission (you must have the EIS branch in your Solarsoft distribution). The key step is to format a SPICE wavelength window into a "windata" structure using the routine spice\_getwindata. An example call is:
+''
+IDL> wd=spice\_getwindata(file)   ; choose a wavelength window \\
+IDL> eis\_fit\_template,wd,template  ; create a template for the fit\\
+IDL> eis\_auto\_fit,wd,fit,template=template\\
+IDL> eis\_fit\_viewer,wd,fit
+''
+The routine eis\_fit\_viewer is a GUI-based routine for browsing the fit results. More details on the eis\_auto\_fit suite of routines are available in [[https://doi.org/10.5281/zenodo.6339584
+|EIS Software Note 15]].
+The EIS software enable a number of operations to be performed on windata structures, as described in [[https://sohoftp.nascom.nasa.gov/solarsoft/hinode/eis/doc/eis_notes/21_WINDATA/eis_swnote_21.pdf|EIS Software Note 21]]. For example, eis\_bin\_windata allows spatial binning of the rasters.
+If you have problems running the EIS software on SPICE data, please contact [[https://science.gsfc.nasa.gov/sed/bio/peter.r.young|Dr. Peter Young]].
+===== Fitting a Gaussian to a spatially-averaged spectrum =====
+In this scenario, a spatial region is selected in the raster, perhaps a bright point or a loop, and the spectra are averaged over this region to produce a single, 1D spectrum. Gaussians are then fit to this spectrum. The procedure is as follows:
+''
+IDL> map=spice\_make\_image(file,770.4)   ; for Ne VIII 770.4\\
+IDL> mask=pixel\_mask\_gui(map)   ; GUI routine for selecting pixel mask\\
+IDL> spec=spice\_mask\_spectrum(file,mask)   ; create averaged spectrum\\
+IDL> spec\_gauss\_spice, spec    ; GUI routine for fitting Gaussians
+''
+These routines are modified from routines originally written for Hinode/EIS. Further details can be found in [[https://doi.org/10.5281/zenodo.6339584
+|EIS Software Note 15]].
+===== Using an auto_fit template for mask spectra =====
+The fitting templates created for eis\_auto\_fit can be useful for fitting mask spectra as well. First create the template for the window you are interested in:
+''
+IDL> wd=spice\_getwindata(file)\\
+IDL> eis\_fit\_template,wd,template \\
+''
+Now create the mask spectrum using the procedure described above. You can then apply the template to the mask spectrum by doing:
+''
+IDL> fit=spice\_mask\_auto\_fit(wd,spec,template,chi2=chi2)
+''
+The output structure ''fit'' contains the fit results. The reduced chi-square value for the fit is returned in the optional output. To overplot the fit on the spectrum, do:
+''
+IDL> p=spice\_plot\_mask\_auto\_fit(spec,fit)
+''

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