       Re: Replacing an expression by an expression

• To: mathgroup at smc.vnet.net
• Subject: [mg55651] Re: [mg55625] Replacing an expression by an expression
• From: DrBob <drbob at bigfoot.com>
• Date: Fri, 1 Apr 2005 05:36:25 -0500 (EST)
• References: <200503310624.BAA15217@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Actually, rep DOESN'T appear verbatim in that entry. Look again, and then try this:

Simplify[-(L21*(J12*x14 - J11*
y14)*(J12*(-x32 -
x43) + J11*(y32 + y43)))/(16*A412*J*(J11^2 + J12^2)), (J12*
x14 - J11*y14)*(J12*(x32 + x43) - J11*(
y32 + y43)) == A0*(A1 - A0)]

(A0*(-A0 + A1)*L21)/(16*A412*J*
(J11^2 + J12^2))

Bobby

On Thu, 31 Mar 2005 01:24:56 -0500 (EST), <carlos at colorado.edu> wrote:

> I have a 8 x 8 symbolic matrix B of complicated entries.
> Several partial expressions, however, can be simplified. Sample:
>
> rep= {(J12*x14-J11*y14)*(J12*(x32+x43)-J11*(y32+y43)) -> A0*(A1-A0)};
>
> The left expression appears verbatim in entry B[[1,1]], which is
>
> -(L21*(J12*x14-J11*y14)*(J12*(-x32-x43)+J11*(y32+y43)))/
> (16*A412*J*(J11^2+J12^2))
>
> But when I say B=B/.rep, nothing happens.  For a few entries I could do
> cut and paste by hand:
>
> -(L21*  A0*(A1-A0)    )/
> (16*A412*J*(J11^2+J12^2))
>
> But it get tedious and error prone for 64.  Any suggestions on how to
> get Mathematica to do the replacement?
>
>
>
>

--
DrBob at bigfoot.com

```

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