Multiple sum with iterators that cannot equal
- To: mathgroup at smc.vnet.net
- Subject: [mg19378] Multiple sum with iterators that cannot equal
- From: Eric Spahr <rspahr at worldnet.att.net>
- Date: Sat, 21 Aug 1999 00:04:45 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Using multiple summmation signs with condition 'i "not
equal" j', evaluation stops immediately as 'i' starts as
1 as does 'j'. My formula requires that the 'i's' and
'j's' together:
Sum[Sum[f,{j,1,n}],{i,1,n}] ignore cases where i
= j.
Or as copied from my notebook:
\!\(\(\(\[Sum]\+\(i = 1\)\%n\[Sum]\+\(j = 1\)\%n\)\+\(i
!=
j\)\) \(w\_i\) \(w\_j\) \[Sigma]\_\(i, j\)\)
w\_j\)
How do I solve this without some cumbersome loops.
Many Thanks
Eric Spahr
Cottage Technology rspahr at worldnet.att.net