       symbolic recombination

• To: mathgroup at smc.vnet.net
• Subject: [mg33287] symbolic recombination
• From: "Mark Morrissey" <mmorriss at ou.edu>
• Date: Wed, 13 Mar 2002 03:15:04 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Folks - Below is the mathematica code to try to recombine a sum of  s = u
+ r[1,t] + r[2,t] + r[3,t] + r[4,t] into the symbolic form of    u +
Sum[r[i,t],{i,1,Length[s]}].  Only it doesn't work the way I coded it.  I
tried 'ReleaseHold[Length[x]]', but it didn't work either.  I trying to find
or build generic code for sum recombination.  Any ideas??

In:=
\!\(sum[x_] := \
Plus[y__[w_, t]] \[Rule]
HoldForm[Sum[y[i, t], \ {i, 1, Length[x]}]]\/Length[x]\)

In:=
\!\(R\&_\_t = \(\[Sum]\+\(i = 1\)\%4\((r[i, t] + \[Mu])\)\)\/4 /. \
R[i, t] \[Rule] r[i, t]\  + \ \[Mu]\  // \ Expand\)

Out=
\!\(\[Mu] + 1\/4\ r[1, t] + 1\/4\ r[2, t] + 1\/4\ r[3, t] + 1\/4\ r[4, t]\)

In:=
\!\(R\&_\_t /. sum[Rest[%]]\)

Out=
\!\(\*
RowBox[{"\[Mu]", "+",
RowBox[{\(1\/4\), " ",
TagBox[\(\[Sum]\+\(i = 1\)\%\(Length[1\/4\ r[1, t] + 1\/4\ r[2, t] + \
1\/4\ r[3, t] + 1\/4\ r[4, t]]\)r[i, t]\),
HoldForm]}]}]\)

Thanks - Mark

Mark Morrissey
Associate Professor of Meteorology
Associate State Climatologist for Research
University of Oklahoma
710 Asp Ave, Suite 8
Norman, OK 73069
405 447-8412

```

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