Hi everyone, I downloaded the spectral derivative tool from the following url: http://www.ittvis.com/cod...nk/search.asp?FID=77 I included this .sav file in the ENVI 4.2 save/add folder. After re-booting computer and launching ENVI, "spectral derivative" appears under the "transform" and "spectral" menu's in the ENVI 4.2 menu bar. When I try to use this tool I get the following error: "Attempt to call undefined procedure/function: DERIV" This tool works perfectly in ENVI 4.1, but I get the above error when using ENVI 4.2. Does anyone know of a solution?? Thanks