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MathGroup Archive 2006

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Re: Function of several variables

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72131] Re: [mg72077] Function of several variables
  • From: "Josef Otta" <josef.otta at gmail.com>
  • Date: Wed, 13 Dec 2006 06:39:26 -0500 (EST)
  • References: <200612110954.EAA07090@smc.vnet.net>
  • Reply-to: josef.otta at mensa.cz

Try to do this:

X[m_] := Table[Subscript[x,i], {i, 1, m}];
f[r_?ListQ] := (1/#) &@(Plus @@ r);

f[X[100]]

I hope that it can solve your problem,

Josef Otta


2006/12/11, tlhiv <thenders at gmail.com >:
>
> I have created a list of variables that I would like to make a function
> in terms of by
>
> M = 4;
> X = Table[Subscript[x, i], {i, 1, M}]
>
> Now I would like to make a function f that is a function of each of
> these M variables.  If I were manually create this function without
> taking advantage of iterators, I would do something like
>
> f[Subscript[x,1]_,Subscript[x,2]_,Subscript[x,3]_,Subscript[x,4]_] =
> 1/(Subscript[x,1]+Subscript[x,2]+Subscript[x,3]+Subscript[x,4])
>
> However, my plan is to significantly increase M, and therefore I don't
> want to have to manually define f in this way.  I would like to define
> it in terms of the elements of X and use the Sum in the function
> definition.  In the end I'm going to be solving an optimization problem
> where I try to find the "optimal" choice for these elements of X.  Can
> someone offer a method for accomplishing this function definition?
>
> Thanks,
>
> --
> Troy Henderson
> Assistant Professor
> Department of Mathematical Sciences
> United States Military Academy
> http://www.tlhiv.org
>
>



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