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MathGroup Archive 2004

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RE: Using a Result from NMinimize

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49384] RE: [mg49367] Using a Result from NMinimize
  • From: "David Park" <djmp at earthlink.net>
  • Date: Sat, 17 Jul 2004 06:38:49 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Greg,

Let's say that you have saved the output of NMinimize in answer.

answer = {0.0817747, {rp -> 0.0920851}};

Now all you have to do is use Part to extract the part of the answer that
you want. For example, to extract and use the replacement rule(s)...

rp /. Part[answer, 2]
0.0920851

Or to extract and save the replacement rule...

rpsol = Part[answer, 2]
{rp -> 0.0920851}

You can now substitute in any expression. For example...

rp^2 + Cos[rp];
% /. rpsol
1.00424

You could Set rp directly with

rp = Part[answer, 2, 1, 2]

and then any expressions will be automatically evaluated.

rp^2 + Cos[rp]
1.00424

But then rp is no longer available as a manipulable symbolic variable. If
you try to revaluate NMinimize, rp will now have a value and it won't work.
So many people prefer to stay with the substitution rule and avoid using
Set.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/





From: Gregory Lypny [mailto:gregory.lypny at videotron.ca]
To: mathgroup at smc.vnet.net

Hello Everyone,

When I use NMinimize, it gives the result as the minimum value of the
function and the value of the argument that gets us there, for example,

	{0.0817747, {rp -> 0.0920851}}.

How can I access the second element, that is, the value of the
argument, so that I can use in other computations.  In other words, I
want get at 0.0920851 and strip away the rp ->.

	Regards,

		Greg




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