Re: FindMinimum

• To: mathgroup at smc.vnet.net
• Subject: [mg15840] Re: FindMinimum
• From: Mark Fisher <mefisher at bellsouth.net>
• Date: Fri, 12 Feb 1999 18:40:00 -0500 (EST)
• References: <79m6o0\$3at@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hossein,

one way to handle the problem is to put your function into an If
statement that returns a huge number when its out of bounds

newfun[x_, y_] := If[Abs[x] > 1 || Abs[y] > 1, 10^10,
oldfun[x, y]]

--Mark.

Hossein Kazemi wrote:

> I have an expression that involves the Sign[] function.  For example,
> consider
>
> f=Sign[4.35x-13.57y +(1-x^2-y^2)]-Sign[2.49x-11.18y+(1-x^2-y^2)]+...
>
> I need to find the minimum of this function.  Since the symbolic
> derivatives with respect to x and y do not exist, I have to use
>
> FindMinimum[f,{x,{x0,x1}},{y,{y0,y1}}]
>
> But this does not restrict Mathematica not look outside (-1,1) range for
> solutions,
> where (1 - x^2 - y^2) will not be real.
>
> Is there anyway to find the minimum of a function when symbolic
> derivatives of
> the function do not exist and values outside a range should not be used.
>
> Thank you.
> kazemi at som.umass.edi

```

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