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MathGroup Archive 2001

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Specifying significant figures in FindMinimum

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31027] Specifying significant figures in FindMinimum
  • From: "Toshiyuki \(Toshi\) Meshii" <meshii at mech.fukui-u.ac.jp>
  • Date: Wed, 3 Oct 2001 02:49:15 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello,

I was wondering whether I can specify significant figures in FindMinimum as
one of a calculation condition.
Though AccuracyGoal or PrecisionGoal may be candidates, I am not confident
about that.

Let me explain my problem.
Suppose I want to find a minimum of a function f[x].
And suppose I know that f[x] shows a minimum close to x = 3.55.
In this case, I will usually do

FindMinimum[ f[x], {x, 3.55} ]

The answer Mathematica returns is like "f[x] shows minimum at x =
3.58123456."

I do not need this.
I just want to find a minimum of f[x] for 3 significant figures for x, like
x = 3.58.
In other words, I am satisfied if I just know that

f[3.58] < f[3.57]
f[3.58] < f[3.59]

I prefer calculation of f[x] in WorkingPrecision, but search in x for 3
significant figures is enough.

Can someone help me on my problem?

********************************************************
   Toshiyuki (Toshi) Meshii  meshii at mech.fukui-u.ac.jp
    Department of Mechanical Engineering
    Fukui University, 3-9-1 Bunkyo, Fukui, 910-8507, JAPAN
     Tel & Fax +81-776-27-8468
     http://mech.fukui-u.ac.jp/~meshii/meshii.htm
********************************************************





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