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Re: Function of several variables

  • To: mathgroup at
  • Subject: [mg72135] Re: Function of several variables
  • From: dh <dh at>
  • Date: Wed, 13 Dec 2006 06:39:37 -0500 (EST)
  • References: <eljaik$7dv$>

Hi Troy,

in Mathematica you have the possibility to treat arguments "block-wise" 

instead of piecewise. Consider e.g.:

fun[x__] := 1/(Plus[x]) (note the 2 underscores)

here we specified that we have 1 or more arguments. We could now call 

fun like: fun[1],fun[1,2],fun[1,2,3] e.t.c.


tlhiv wrote:

> 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



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