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MathGroup Archive 1998

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Re: Linearization

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15130] Re: Linearization
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Wed, 16 Dec 1998 03:11:09 -0500
  • References: <754vm1$jgc@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Christoph,

Linearize[poly_, vars_] :=
  Module[{u},
    Expand[ poly, Alternatives@@vars] /. Thread[vars -> (vars u)] /.
      {u^n_ -> 0, u -> 1}]

Test:

Linearize[1 + u + (a + b)x + x u + x^2 + u^2, {x, u}]

1 + u + (a + b) x

Allan
---------------------
Allan Hayes
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565


Christoph wrote in message <754vm1$jgc at smc.vnet.net>...
> Howdy,
>
>is there any nice way to linearize an equation in Matematica?
>
>e.g.:
>i have a function
>
>f[x,y]
>
>if i do
>Normal[Series[f[x,y],{x,0,1},{y,0,1}]]
>
>i will still have a term containing x*y, but if x and y are small i can
>discard this term. Can mathematica discard term automaticly?
>
>
>Christoph
>
>PS:  THis is an example, I have a function with seven variables and
>don't wan't to pick the correct ones manualy.
>
>PPS: could you pleas also mail me?
>
>



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