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MathGroup Archive 1999

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Re: Plot vs FindMinimum

  • To: mathgroup at smc.vnet.net
  • Subject: [mg18379] Re: [mg18314] Plot vs FindMinimum
  • From: "Andrzej Kozlowski" <andrzej at tuins.ac.jp>
  • Date: Wed, 30 Jun 1999 14:13:36 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

You can use Plot to find numerical maximum or minimum. Here is an example:

In[1]:=
gr=Plot[x^3-3x+1,{x,-1.5,1.5}]
(graph)
In[2]:=
Cases[gr[[1,1,1,1]],{_,Max[Transpose[gr[[1,1,1,1]]][[2]]]}]
Out[2]=
{{-0.999918, 3.}}

In[3]:=
Cases[gr[[1,1,1,1]],{_,Min[Transpose[gr[[1,1,1,1]]][[2]]]}]
Out[3]=
{{0.999559, -0.999999}}
--
Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp
http://eri2.tuins.ac.jp


----------
>From: "Joaquin Gonzalez de Echavarri" <jge at clientes.euskaltel.es>
>To: mathgroup at smc.vnet.net
>Subject: [mg18379] [mg18314] Plot vs FindMinimum
>Date: Sun, Jun 27, 1999, 8:07 AM
>

> I'm trying to find the minimum of a function practically flat in a very
> large intervall, after that it falls suddenly, reaches the minimun and rises
> very fast again.
>
> I'm able to see the function and the minimun with Plot in a fraction of
> second but is very dificult and it takes a lot of time to find it with
> FindMinimum, my question is:
>
> Is it not possible to use the same algorithm that Plot uses for finding the
> value of the minimun?
>
> What's that algorithm?
> TK and BR
>
> Joako
>
>
>
> 


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