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MathGroup Archive 1997

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Re: Turning the elements of a list into the arguments of a function.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg8857] Re: Turning the elements of a list into the arguments of a function.
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Tue, 30 Sep 1997 20:16:17 -0400
  • Organization: University of Western Australia
  • Sender: owner-wri-mathgroup at wolfram.com

Scott Morrison wrote:

> I need to be able to convert
> f[q, {{a,b}, {c,d}}] into f[q, {a,b}, {c,d}]
> 
> If the problem were to convert f[{{a,b},{c,d}}] into f[{a,b}, {c,d}], I know
> I could do this with Apply, as Apply[f, {{a,b},{c,d}}], but having that
> first argument is making my life difficult.
> 
> What I am actually trying to do is use FindMinimum with a variable number of
> variables, so I tried FindMinimum[expr, Table[{g[i], 0}, {i, 1, n}] sort of
> thing, but this puts all the variables and their starting values in one huge
> list.

You need to use Evaluate (because FindMinimum is HoldAll) and Sequence:

  In[1]:= FindMinimum[g[1]^2-2g[1]+2g[2]^2, 
			Evaluate[Sequence@@Table[{g[i], 0}, {i, 1, 2}]]]

  Out[1]= {-1., {g[1] -> 1., g[2] -> 0.}}

Cheers,
	Paul 

____________________________________________________________________ 
Paul Abbott                                   Phone: +61-8-9380-2734
Department of Physics                           Fax: +61-8-9380-1014
The University of Western Australia           
Nedlands WA  6907                     mailto:paul at physics.uwa.edu.au 
AUSTRALIA                             http://www.pd.uwa.edu.au/~paul

            God IS a weakly left-handed dice player
____________________________________________________________________


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