Hi, there I want to write several 2-D arrays into a dateset as several ‘bands’, not several 'datesets' in a file. I use HDF_SD_START  with keywords  /CREATE  to create a HDF file, and use HDF_SD_CREATE to create a dateset in the generated file. Now I have some (suppose 7) 2-D arrays that can be wrote into the file. What I want is to write these 7 array into the dateset as '7 bands in one dataset', not as 7 datesets in this file. that is to say, if I use ENVI_FILE_QUERY  to check the NB of the file, I want the result is 7, not 1. How can I do it in IDL? thanks