Re: Summing elements within a List or Array

• To: mathgroup at smc.vnet.net
• Subject: [mg69573] Re: Summing elements within a List or Array
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Fri, 15 Sep 2006 06:47:46 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <eebfs6\$57q\$1@smc.vnet.net>

```John Adeosun wrote:
> Hello Everyone,
>
> I generated an intended list of real numbers using Mathematica 5.2, say
> "alist", that looks like:
>
> alist = {{0}, {{1.2},0}, {{2.3},{1.2},0},{{3.4},{2.3},{1.2},0},
> ................{{99.0},{98.9},{97.8},.......,0}}
> (In Matrix form, this "alist" can be shown as a LowerDiagonal Matrix)
>
> Meanwhile, my present goal is to then program using Mathematica to obtain a
> list, say "aalist", having each element equal to the sum of the elements in
> each(corresponding) sublist of the original list "alist." That is,
>
> aalist  = {0, 1.2, 3.5, 6.9,...........}
>
> In essence, it is like reducing, say, 100 by 100 matrix to 100 by 1 matrix
> via summing operation.
>
>  I programmed using some summing operations/functions in Mathematica to no
> avail. I don't know what I 'm doing wrong.
>
> Can anyone help with this problem?
>
> Thanks,
>
> John.
>

alist = {{0}, {{1.2}, 0}, {{2.3}, {1.2}, 0}, {{3.4}, {2.3}, {1.2}, 0},
{{99.}, {98.9}, {97.8}, 0}};

aalist = Flatten[Apply[Plus, alist, {1}]]

--> {0, 1.2, 3.5, 6.9, 295.7}

Jean-Marc

```

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