Re: Summing elements within a List or Array
- To: mathgroup at smc.vnet.net
- Subject: [mg69538] Re: Summing elements within a List or Array
- From: dimmechan at yahoo.com
- Date: Fri, 15 Sep 2006 06:44:51 -0400 (EDT)
- References: <eebfs6$57q$1@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)
http://www.verbeia.com/mathematica/tips/HTMLLinks/Tricks_A-K_3.html
***(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
Î?/Î? John Adeosun ÎγÏ?αÏ?ε:
> 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.