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MathGroup Archive 2006

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Re: decrementing problem

  • To: mathgroup at
  • Subject: [mg72314] Re: [mg72293] decrementing problem
  • From: Murray Eisenberg <murray at>
  • Date: Tue, 26 Dec 2006 05:14:23 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <>
  • Reply-to: murray at

Why bother with a For loop when Mathematica can handle the details for you:

   Sum[U[[i,j]] X[[j]],{i,n-1,1,-1},{j,i+1,n}]

jltrahan at wrote:
> Hi,
> I am having a really difficult time with decrementing values in my For
> loop. I have tried i--, --i, i-=1, i=i-1, and nothing is working. The loop
> is as follows:
> For[i=n-1, i<=1, i--, summ=0;
>    For[j=i+1, j<=n, j++, summ=summ + U[[i,j]]*X[[j]]]
> ]
> When I try to print i or j, nothing shows up.
> Can anyone please help?
> Thank you in advance,
> Jamie

Murray Eisenberg                     murray at
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

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