Summation convention
- To: mathgroup at christensen.cybernetics.net
- Subject: [mg204] Summation convention
- From: corcoran (Stephen Corcoran) <corcoran%markov.stats at comlab.oxford.ac.uk>
- Date: Sat, 19 Nov 1994 14:50:11 +0000
Dear Mathgroupers,
I wonder if you could help me,
I need to set up a rule of the following form,
rule = {b[a[x_]] -> d[a[y],a[x]] c[a[y]]},
where a[y] must differ from all other indices a[k] used so far.
My application involves expressions involving use of the summation
convention which I would like to manipulate using Mma. Thus, in "rule"
given above, the RHS is interpreted as being summed over the index a[y].
I need to ensure that, in any given complicated expression,
that if
e = b[a[1]] b[a[2]]
and each b[a[j]] (j=1,2) is to be replaced by a term involving summation using
the above "rule", that the indices using in each summation are different. One
thing I thought of involved incrementing the summation index y in "rule" each
time I used it, but this would not work as if I write
f = e /. rule
"rule" is applied twice before I have a chance to increment y.
Any suggestions?
(I am actually away for the next week, but I look forward to reading
email on my return!),
Thanks,
Stephen
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Stephen Corcoran, email: corcoran at stats.ox.ac.uk (internet)
Dept. of Statistics, corcoran at uk.ac.ox.stats (janet)
University of Oxford,
1, South Parks Road phone: (0865) 272879
OXFORD, OX1 3TG fax: (0865) 272595
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