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From: bdb112@csc.anu.edu.au
Newsgroups: comp.lang.idl-pvwave
Subject: How can I integrate? (easy question?)
Message-ID: <1991Mar20.233728.1@csc.anu.edu.au>
Date: 20 Mar 91 12:37:28 GMT
Sender: news@newshost.anu.edu.au
Organization: Computer Services, Australian National University
Lines: 7

How can I efficiently do a running sum of a vector (integrate)?  The explicitly
coded version (IDL v2)  
for i=1,n-1  x(i)=x(i) + x(i-1) achieves the desired effect, but takes (VS3100)
1 second for a 2000 element array compared to .01 sec for z=x+x, a similar
number of operations.  This is such an obvious thing to do that I must be
missing something obvious - I can't find it in the userlib either (just
deriv).