Hi, I'm very new in IDL. I want to calculate NDVI indice for a lot of images with got from private company. I found in this forum a pro code and i tryed to adapt it but it not working. Please check and tell me what is wrong. pro ndvi_batch compile_opt idl2 ;set up path to input and output files ;input_path = 'X:\JEdi_D2\GrassService\Siguldas_nov\Process\140708\112717_2' ;change to output directory where I want the processed files to be placed cd, 'X:\JEdi_D2\GrassService\Siguldas_nov\Process\140708\112717' ; search for data files in the specified directory files = FILE_SEARCH('X:\JEdi_D2\GrassService\Siguldas_nov\Process\140708\112717\CASI_2014_07_08_112717_g.pix', 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 ;set pos array for calculating NDVI pos = [21,10] - 1 ;set the output file names by stripping out the base name and appending 'ndvi.img' out_name = file_basename(filename,'.dat')+'_NDVI.dat' ;call the doit envi_doit, 'ndvi_doit', $ fid=fid, pos=pos, dims=dims, $ /check, o_min=0, o_max=255, $ out_name=out_name, r_fid=r_fid endfor end IDL> ndvi_batch % Compiled module: NDVI_BATCH. % Expression must be a scalar or 1 element array in this context: . % Execution halted at: NDVI_BATCH 18 X:\JEdi_D2\!IDL_darbs\ndvi_batch.pro % $MAIN$