Re: Summing elements within a List or Array

• To: mathgroup at smc.vnet.net
• Subject: [mg69728] Re: Summing elements within a List or Array
• Date: Thu, 21 Sep 2006 07:31:57 -0400 (EDT)
• References: <eebfs6\$57q\$1@smc.vnet.net> <eee0i8\$6h0\$1@smc.vnet.net>

```Thanks for the useful suggestion...It works well.
John.
<dimmechan at yahoo.com> wrote in message news:eee0i8\$6h0\$1 at smc.vnet.net...
> ***You can work as follows:
>
> In[96]:=
> Flatten[Apply[Plus,alist,1],1]
> Out[96]=
> {0,1.2,3.5,6.9}
>
> ***or in compact form
>
> In[95]:=
> Plus@@@alist//Flatten
> Out[95]=
> {0,1.2,3.5,6.9}
>
> ***As you can see in the Help Browser and also in (Ted Ersek's Tips and
> Tricks)
>
> ***(f@@lst)  is normally equivalent to Apply[f, expr] and  (f@@@lst)
> is normally equivalent to Apply[f, lst, 1] as demonstrated below
>
> In[103]:=
> lst={1,2,3};
>
> ln[104]:=
> {Apply[f,lst]==f@@lst,Apply[f,lst,1]==f@@@lst}
> Out[104]=
> {True,True}
>
> ***BTW can you tell me how you generate your alist within Mathematica?
>
>
> Dimitris Anagnostou
>
>
>> 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.
>

```

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