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Re: reading binary files [message #54512 is a reply to message #49280]

Tue, 19 June 2007 06:00

Wox
Messages: 184
Registered: August 2006

Senior Member

On Tue, 19 Jun 2007 00:49:17 -0700, Vince Oliver
<vince@complex.elte.hu> wrote:

> Firest try was using Assoc function. It was somehow natural choice
> since the number of spectra is large. So:
>
> data = 'c:\users\spectra10.bin'
> spectra = Assoc(lun, Fltarr(2,7323))
> aSpectra = spectra[0]
> print, aSpectra[0,0],aSpectra[1,0]
> print, aSpectra[0,7322],aSpectra[1,7322]
> print
> aSpectra = spectra[1]
> print, aSpectra[0,0],aSpectra[1,0]
> print, aSpectra[0,7322],aSpectra[1,7322]
>
> The outout is
>
> 8.20937e-041 91.0000
> 1.07971e-021 3.60000e+008
>
> 2.11875e-022 8.20937e-041
> 2.57653e-020 2.40000e+008
>
>
> It was clear that I should put an offset keyword in Assoc like spectra
> = Assoc(lun, Fltarr(2,7323),4). The output in this case is:
>
> 91.0000 2.04773e-023
> 3.60000e+008 2.11875e-022
>
> 8.20937e-041 8.20937e-041
> 2.40000e+008 5.08605e-021
>
>
> So the 1st spectrum is properly read out but the second not. It seems
> that there is an offset between each spectra. How to read out spectra
> properly in this case?
>
> ########################################

From IDL's help:

"Unformatted data files generated by FORTRAN programs under UNIX
contain an extra long word before and after each logical record in the
file. ASSOC does not interpret these extra bytes but considers them to
be part of the data. This is true even if the F77_UNFORMATTED keyword
is specified..."

I have no experience with this, but what happens if you use (e.g. for
3rd spectrum):

specnr=2
nlen=7323
n=2*nlen+1
specoff=n*specnr*4
spectra = Assoc(lun, Fltarr(n),specoff)

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[Message index]

		Reading binary files made by Python By: Liberum on Mon, 10 July 2006 02:45
		Re: reading binary files By: Vince Oliver on Tue, 19 June 2007 09:10
		Re: reading binary files By: Paul Van Delst[1] on Tue, 19 June 2007 08:28
		Re: reading binary files By: Vince Oliver on Tue, 19 June 2007 08:06
		Re: reading binary files By: Paul Van Delst[1] on Tue, 19 June 2007 07:47
		Re: reading binary files By: Vince Oliver on Tue, 19 June 2007 07:16
		Re: reading binary files By: Wox on Tue, 19 June 2007 06:06
		Re: reading binary files By: Wox on Tue, 19 June 2007 06:00

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