;make some fake data data = indgen(25) + 10 ;open a file openw, lun, filename,/get_lun ;print to file for i = 0, n_elements(data) - 1 do printf, lun, data[i] ;close file and free file pointer free_lun, lun   of course, if you're brave, newer versions of IDL on windows can write excel files directly through an ActiveX control. Try searching the user code page for IDL64_Read_Excel11.zip (even though it says read excel i'm reasonably sure the write routines are in there too).      

I know this is a very old post, but still extremely relevant. There are many forums with links to 'IDL64_Read_Excel11.zip' and it is nowhere to be found, including any related info. Where can I find this file or related info on how to read an excel file (converting to .csv isn't possible since it must be done in code). Thanks

Hi Jeremy, Those code libraries are no longer available per new policies that we have here at Exelis VIS. They have actually been unavailable for a couple years. You may be able to find it somewhere else on the internet, but we are no longer allowed to distribute those code libraries anymore.

For those who can utilize data written by IDL to a CSV file , you might look into the IDL routine "WRITE_CSV": http://www.exelisvis.com/docs/WRITE_C... See also the corresponding "READ_CSV" and "QUERY_CSV" routines.