| Re: continuum normalized spectra [message #82998] |
Sun, 03 February 2013 06:20  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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idlhelp writes:
> But I am not sure that I am doing the continuum normalization to unity in a right way.
Well, unless this has a specific meaning in your field (astronomy?), I
would take "normalization to unity" to mean divide the result by its
maximum value.
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: continuum normalized spectra [message #83000 is a reply to message #82998] |
Sun, 03 February 2013 00:09  |
abc
Messages: 46
Registered: March 2011
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Member |
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On Saturday, February 2, 2013 7:42:39 PM UTC+1, David Fanning wrote:
> idlhelp writes:
>
>
>
>> I want to write a program to fit a linear local continuum of absorption line, and plot the spectrum with continuum drawn and the spectrum normalized by the continuum. And than I want to Fit a local continuum using data in the wavelength ranges 1800-1820 and 2020-2040 angstroms.
>
>>
>
>> Does anyone know that how can I do that
>
>
>
> Yes, probably. But, not without a hell of a lot more information. :-)
>
>
>
> Cheers,
>
>
>
> David
>
>
>
>
>
>
>
> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
Hi David,
ok so here is the information. This is how I am doing :-)
; filename - the filename of the input spectrum
; column - the number of columns in the file
; row - the number of rows in the file
; boxsize - the size of the boxcar for the smoothing function
; dofit - the user keyword
; dofityes - the variable containing the input parameter
data = fltarr(column, row)
; open the file as read only
openr,lun,filename,/get_lun
; read the data from the file into the array
readf,lun,data
; close the file
close,/all
wave=reform(data(0,*))
flux=reform(data(1,*))
; This creates a new array containing the results generate
; by the smooth function.
smoothed_flux = smooth(flux,boxsize)
; check to see if the user would like to fit the continuum
if keyword_set(dofityes) then begin ; this check the dofit keyword
; fit velocity and smoothed_flux, using a 1st order polynomial.
result = poly_fit(wave,smoothed_flux,1)
; generate the continuum with the results from the fit
continuum = result(0) + result(1)*wave
end
But I am not sure that I am doing the continuum normalization to unity in a right way. Because when I make plots the contunum level is higher than the unity.
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| Re: continuum normalized spectra [message #83097 is a reply to message #83000] |
Sun, 03 February 2013 06:22 |
Mats Löfdahl
Messages: 263
Registered: January 2012
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Senior Member |
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Den söndagen den 3:e februari 2013 kl. 09:09:20 UTC+1 skrev idlhelp:
> On Saturday, February 2, 2013 7:42:39 PM UTC+1, David Fanning wrote:
>
>> idlhelp writes:
>
>>
>
>>
>
>>
>
>>> I want to write a program to fit a linear local continuum of absorption line, and plot the spectrum with continuum drawn and the spectrum normalized by the continuum. And than I want to Fit a local continuum using data in the wavelength ranges 1800-1820 and 2020-2040 angstroms.
>
>>
>
>>>
>
>>
>
>>> Does anyone know that how can I do that
>
>>
>
>>
>
>>
>
>> Yes, probably. But, not without a hell of a lot more information. :-)
>
>>
>
>>
>
>>
>
>> Cheers,
>
>>
>
>>
>
>>
>
>> David
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>>
>
>> --
>
>>
>
>> David Fanning, Ph.D.
>
>>
>
>> Fanning Software Consulting, Inc.
>
>>
>
>> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
>>
>
>> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
>
>
>
>
>
> Hi David,
>
> ok so here is the information. This is how I am doing :-)
>
>
>
>
>
> ; filename - the filename of the input spectrum
>
> ; column - the number of columns in the file
>
> ; row - the number of rows in the file
>
> ; boxsize - the size of the boxcar for the smoothing function
>
> ; dofit - the user keyword
>
> ; dofityes - the variable containing the input parameter
>
>
>
>
>
>
>
> data = fltarr(column, row)
>
>
>
> ; open the file as read only
>
> openr,lun,filename,/get_lun
>
>
>
> ; read the data from the file into the array
>
> readf,lun,data
>
>
>
> ; close the file
>
> close,/all
>
>
>
>
>
> wave=reform(data(0,*))
>
> flux=reform(data(1,*))
>
>
>
>
>
> ; This creates a new array containing the results generate
>
> ; by the smooth function.
>
> smoothed_flux = smooth(flux,boxsize)
>
>
>
>
>
> ; check to see if the user would like to fit the continuum
>
> if keyword_set(dofityes) then begin ; this check the dofit keyword
>
>
>
> ; fit velocity and smoothed_flux, using a 1st order polynomial.
>
> result = poly_fit(wave,smoothed_flux,1)
>
>
>
> ; generate the continuum with the results from the fit
>
> continuum = result(0) + result(1)*wave
>
>
>
>
>
> end
>
>
>
>
>
> But I am not sure that I am doing the continuum normalization to unity in a right way. Because when I make plots the contunum level is higher than the unity.
As far as I can see, you don't do any normalization at all. You calculate the fit, but you never operate on the original (or smoothed) spectrum with that fit. I guess you need to divide the spectrum with the fit.
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