Re: variable range

[Pedro Gonnet <pedro at vis dot ethz dot ch>]

Given your example function:

	f(x) = 3*(x-4)*(x-4)+2
	      = 3*x^2 - 24*x + 50

We can define a funciton

	f*(v) = 3*v^4 - 24*v^2 + 50
	       = f(v^2)

The minimum positive value for f(x) is then arg(min(f*(v)))^2, which,
per definition, is always postive for real values of v.

On Tue, 2003-07-29 at 12:12, Przemyslaw.Sliwa@ecb.int wrote:
> Could you give me any example???
> I do not have any idea how to proceed with it.
> 
> Thanks,
> 
> Przem
> 
> 
> 
> Hello,
> 
> a good idea is to make a change of variable in such a way that
> the new variable are unconstrained.
> 
> I hope that helps,
> Jerome
> 
> Sang-Joon Lee wrote: 
> 	Hi,
> 	
> 	In using the GSL "Multidimensional Minimization" algorithms, I would
> like
> 	to limit the range of variables.  For instance, in a function,
> 	f(x)=3*(x-4)*(x-4)+2, I would like to make x be a positive real
> number.
> 	I would appreciate if you let me know how to do this.
> 
> 	Sincerely yours,
> 	
> 	Sang-Joon Lee
> 	
> 	
> 	
> 
> 
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