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Topic: how to set initial values to symbolic variable array?
Replies: 3   Last Post: Mar 2, 2013 2:34 AM

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Murray Eisenberg

Posts: 2,100
Registered: 12/6/04
Re: how to set initial values to symbolic variable array?
Posted: Feb 28, 2013 9:24 PM
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Not clear why you're calling f a function, or why you "manually" add the four elements of the array. To answer your question:

arr = Array[a, 4];
f = Total[arr];
f /. a[_] -> 1


On Feb 27, 2013, at 11:45 PM, Jon <devout1977@gmail.com> wrote:

>
> Dear All,
>
> Suppose I defined a symbolic variable array as
>
> Array[a,4]
>
> and defined a function as
>
> f = a[1] + a[2] + a[3] + a[4]
>
> I need to evaluate the value of f in the following way,
>
> f/.{a[1]->1,a[2]->1, ...}
>
> but specify each element of the array one by one is very troublesome, and I
> wonder whether there is something like a group definition like
>
> f/.{a[1:4]->1}
>
> to define the four variables at the same time with the same value.
>
> Thanks for your help,
>
> Sincerely,
> John
>


---
Murray Eisenberg murray@math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2838 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305









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