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Re: Non trivial substitution in a very long output

• To: mathgroup at smc.vnet.net
• Subject: [mg123165] Re: Non trivial substitution in a very long output
• From: Marco Maso <demind at gmail.com>
• Date: Fri, 25 Nov 2011 04:55:03 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201111241156.GAA28999@smc.vnet.net>

Ok, this is not exactly what I was looking for but gave me an idea on
how I can find a workaround to this problem...I will report here in a
while with the outcome!

Thanks

Marco


Il giorno Thu, 24 Nov 2011 11:30:25 -0600
DrMajorBob <btreat1 at austin.rr.com> ha scritto:

> It seems to work fine in this example:
>
> piece = Abs[b41]^2 + Abs[b51]^2 + Abs[b61]^2 +
>     Abs[(b61 x1 + b51 x2 + b41 x3)/x4]^2 +
>     Abs[(b61 x2 + b51 x3 + b41 x4)/x1]^2 +
>     Abs[(b61 x1 x3 + b51 (x2 x3 - x1 x4) + b41 (x3^2 - x2 x4))/
>        x4^2]^2 +
>     Abs[(b61 (x1 x3^2 - x1 x2 x4) +
>          b51 (x2 x3^2 - x2^2 x4 - x1 x3 x4) +
>          b41 (x3^3 - 2 x2 x3 x4 + x1 x4^2))/x4^3]^2;
> expr = piece + piece^2 - Sin@piece;
> expr //. piece -> p
>
> p + p^2 - Sin[p]
>
> Bobby
>
> On Thu, 24 Nov 2011 05:56:33 -0600, Demind <demind at gmail.com> wrote:
>
> > Hello, my name is Marco. I am experiencing an annoying problem
> > using Mathematica. I am dealing with a huge expression, some
> > hundreds of lines. I can find 3/4 patterns repeating inside it, and
> > I would really like to substitute thme with dummy variables, namely
> > D1, D2, D3, D4. I'm expecting the readibility of the equation to be
> > improved after this process. As it is right now, it's totally
> > unreadable. I went through past topics to find solutions to my
> > problem, but unfortunately none of the tricks I tried worked
> > (mainly /. and //.).
> >
> > I give you a sample of what I would like to do, hoping that someone
> > will give me some help:
> >
> > In my equation, Out[1] = ...
> > the following pattern is repeated:
> >
> > Abs[b41]^2 + Abs[b51]^2 + Abs[b61]^2 + Abs[(b61 x1 + b51 x2 + b41 
> > x3)/x4]^2 + Abs[(b61 x2 + b51 x3 + b41 x4)/x1]^2 + Abs[(b61 x1 x3 +
> > b51 (x2 x3 - x1 x4) + b41 (x3^2 - x2 x4))/x4^2]^2 + Abs[(b61 (x1
> > x3^2 - x1 x2 x4) + b51 (x2 x3^2 - x2^2 x4 - x1 x3 x4) + b41 (x3^3 -
> > 2 x2 x3 x4 + x1 x4^2))/x4^3]^2
> >
> > I'm doing:
> >
> > Out[1] //. Abs[b41]^2 + Abs[b51]^2 + Abs[b61]^2 + Abs[(b61 x1 + b51
> > x2 + b41 x3)/x4]^2 + Abs[(b61 x2 + b51 x3 + b41 x4)/x1]^2 +
> > Abs[(b61 x1 x3 + b51 (x2 x3 - x1 x4) + b41 (x3^2 - x2 x4))/x4^2]^2
> > + Abs[(b61 (x1 x3^2 - x1 x2 x4) + b51 (x2 x3^2 - x2^2 x4 - x1 x3
> > x4) + b41 (x3^3 - 2 x2 x3 x4 
> > + x1 x4^2))/x4^3]^2 -> D1
> >
> > Here the text is attached in "InputForm", where in my notebook I
> > have it in "StandardForm" (I use the latter in my notebook, but
> > here I can't reproduce it for obvious reasons). I tried to use the
> > command above both in StandardForm and in InputForm with no result.
> >
> > Thank you very much
> >
> > Marco
> >
>
>

• References:
  • Non trivial substitution in a very long output
    • From: Demind <demind@gmail.com>