Archiving spectral line data at AO

Why use IDL rather than a DBMS??

• DBMS's seem to be ASCII oriented. Once they give you the subset of the data you want, you need to have another program process it. Binary data is normally treated as opaque (they dont' know how to interpret it).

 
• The WHERE command of IDL will create a subset of an array using any expression you can generate in idl. The search and extraction of the data is fast (instantaneous to the user with an array of 325000 entries).

 
• idl example: find all the scans using lbw (rcv=5) below 10 degrees za with their center frequency within 5 Mhz of the airport radar frequencies: 1330,1350.

 
ind=where((slar.rcvnum eq 5) and (slar.zaavg lt 10.) and              ((abs(slar.freq-1330) lt 5) or (abs(slar.freq-1350) lt 5))
 
• Once idl has created the subset of indices, it can also be used to input, process, and then plot the results. It is a programming language so you can automate what you want to do.