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Hi guys,
Im just new in using IDL. Last time I posted here, I got help from this forum on how to use MATH DO IT for vegetation indices calculation, i.e. NDVI and LSWI which uses 2 bands for calculation (red and NIR). It worked! Thank you.
I tried using the same script for "EVI" and just changed the equation and bands since it uses 3 bands for calculation (RED,NIR,BLUE bands).
QUESTION about MATH DO IT: Does it work for 3 input bands? Or its just limited to 2 input bands? If any of you have time, can you help me please to figure out whats wrong with the script?
Or if you have any sugestion on what I can use for EVI calculation. Im processing tons of images, and doing it one by one in ENVI Band math would consume lots of time.
Thank you very much in advance.
Here's the script I used and the error:
pro evi_math_doit
compile_opt idl2
input_path = 'E:\aRiceMapping\xENVI_test\Sinu\2007\'
cd, 'E:\aRiceMapping\xENVI_test\Sinu\EVI\'
files=FILE_SEARCH(input_path+'*.tif', count=count)
IF(count EQ 0)THEN BEGIN
PrintF, 'No files were found to process'
ENDIF
for i=0, count-1 do begin
envi_open_file, files[i], r_fid=fid
if(fid eq -1) then begin
envi_batch_exit
return
endif
envi_file_query, fid, dims=dims, ns=ns, nl=nl, fname=filename
t_fid=[fid,fid]
;set pos array for calculation EVI
pos = [2,3,0]
exp = '2.5*(b1-b2)/(b1+(6*b2)-(7.5*b3)+1)'
;set the oputput filenames by stripping out the base name and appending 'ndvi.img'
out_name = file_basename(filename,'.tif')+'_lswi.tif'
;call the doit
envi_doit,'math_doit',$
fid=t_fid, pos=pos, dims=dims,$
exp=exp, out_name=out_name, $
r_fid=r_fid
endfor
end
ERROR:
math_doit: An error has occured during processing
Error: "Attempt to subscript FID with I is out of range."
The result may be invalid
Sincerely,
ONYANG
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