       Re: decrementing problem

• To: mathgroup at smc.vnet.net
• Subject: [mg72314] Re: [mg72293] decrementing problem
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Tue, 26 Dec 2006 04:47:00 -0500 (EST)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <200612181156.GAA02194@smc.vnet.net>

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

n=5;
U=Table[Random[Real],{i,n},{j,n}];
X=Table[Random[Real],{j,n}];
Sum[U[[i,j]] X[[j]],{i,n-1,1,-1},{j,i+1,n}]
0.832632

jltrahan at mail.usf.edu 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.
>
> Jamie
>

--
Murray Eisenberg                     murray at math.umass.edu
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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