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MathGroup Archive 2006

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Re: How to treat this false singular point?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68427] Re: [mg68406] How to treat this false singular point?
  • From: Takashi YOSHINO <tyoshino at toyonet.toyo.ac.jp>
  • Date: Sat, 5 Aug 2006 03:46:03 -0400 (EDT)
  • References: <200608031007.GAA15885@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Use Limit.  For example, define f[x_]

f[x_] := Limit[(xi - x1)Log[Abs[xi -
            x1]] + (xi - x2)Log[Abs[xi - x2]], xi -> x, Assumptions -> {
            Element[x1, Reals], Element[x2, Reals]}]

and estimate f[x1].  The output is like
((x1 - x2)*Log[(x1 - x2)^2])/2


simon yang wrote:
> Dear everyone,
> I have a function:
> f[x_]:=(x-x1)Log[Abs[x-x1]] + (x-x2)Log[Abs[x-x2]] + ... +
> (x-xn)Log[Abs[x-xn]],
> {x1,x2,...,xn}={100,200,300,...} for instance
> How to get value: f[x] as there are different singular at different x?
> I know at x=xn, f[x]==1, But Mathematica return: "Indeterminate", What
> should I do?
>  what others do in C++, Fortran ?
> 


-- 
Takashi Yoshino


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