Rainer Bars
New Member
Posts:5  
| 21 Dec 2016 06:46 AM |
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Hellos,
I'm looking for a tool or an existing ENVI script to calculate a 1st degree derivative on all spectra of a hyperspectral image.
I assume many others have needed this, so a script likely exists. I couldn't find anything googling around. And as IDL isn't available, I can't use spectral math to call DERIV(s1) on a BIP image, which would do the same thing.
If anything doesn't exist, then it's back to the code editor :-)
Thanks in advance and cheers,
Rainer
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Mari Minari
Veteran Member
Posts:1961 
| 21 Dec 2016 08:53 AM |
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If you have a spectral plot displayed in ENVI, or a spectral library, you can use Spectral Math and IDL's DERIV function to calculate the derivatives of a spectrum. For example, in Spectral Math use:
deriv(s1)
and map the s1 variable to the spectrum or to a spectral library file using Map variable to input file.
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Rainer Bars
New Member
Posts:5
| 22 Dec 2016 03:42 AM |
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Hello,
if I use deriv(s1) in spectral math under ENVI, I get an error message saying
"You have entered an invalid expression. Check for syntax errors or undefined procedures and functions and try again."
I assume it's because I am running ENVI only?
Best,
Rainer
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Mari Minari
Veteran Member
Posts:1961
| 22 Dec 2016 05:56 AM |
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What version of ENVI are you running and on what OS? I can run this equation in ENVI runtime:
deriv(s1)
You should still be able to use some IDL operators in Spectral Math or Band Math with runtime.
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Rainer Bars
New Member
Posts:5
| 22 Dec 2016 07:00 AM |
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I am running ENVI 5.3.1 on win 7 64-bit.
I just did another check: deriv(s1) works on the spectral math of the "new" GUI, but not in the classic interface! I think we are satisfied with that, so thank you!
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