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Re: FindMinimum constraints

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92963] Re: FindMinimum constraints
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Tue, 21 Oct 2008 01:44:03 -0400 (EDT)
  • Organization: The Open University, Milton Keynes, UK
  • References: <gdja4r$idt$1@smc.vnet.net>

dantimatter wrote:

> I have a large and complicated model for which I'm using the
> FindMinimum function to find a solution.  The solution consists of 101
> numbers a[i] (i goes from 0 to 100), all greater than zero, and the
> search for each a[i] begins at 0.001:
> 
> sol = FindMinimum[{model, Table[a[i] > 0,{i, 0, 100}]}, Table[{a[i],
> 0.001},{i, 0, 100}]];
> 
> The line of code that I'm showing here works great.  My problem now is
> that I'd like to add an additional constraint:  that a[100] ==
> 0.5*(a[0]+a[25]).  I can't for the life of me figure out how to
> include this added constraint in the line of code that already works.
> I get errors when I use Append[] to the Table. I would appreciate any
> thoughts on this.

Using *Join* should do the trick. For instance,

sol = FindMinimum[{model,
    Join[{a[100] == 0.5*(a[0] + a[25])},
     Table[a[i] > 0, {i, 0, 100}]]}, Table[{a[i], 0.001}, {i, 0, 100}]]

Regards,
-- Jean-Marc


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