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Re: copying values of entries between matrices
*To*: mathgroup at smc.vnet.net
*Subject*: [mg77977] Re: copying values of entries between matrices
*From*: Norbert Marxer <marxer at mec.li>
*Date*: Thu, 21 Jun 2007 05:28:56 -0400 (EDT)
*References*: <f5atd0$an9$1@smc.vnet.net>
On 20 Jun., 11:52, "text.tex" <Clausena... at gmail.com> wrote:
> Hi,
> here is my problem:
> I have a 18x18 matrix called entMatr.
> I want to copy the values of the elements of the lower left half of
> entMatr into a 171x1 matrix called dOneCol.
> I had tried a 3-nested loop for copying the values from entMatr to
> dOneCol; the current version where I tried to replace the loop over
> the rows of dOneCol with a counter q produces a result, however the
> result is not what I want...
>
> I'd greatly appreciate any pointers how to get this working!
> Thanks,
> Claus
>
> This is what I tried:
>
> <pre>
> (* initialize entMatr *)
> entMatr = Table[Subscript[m, i, j], {i, 18}, {j, 18}];
>
> (* fill the lower left half of entMatr with some values *)
> For[i = 1, i < 18 + 1, i++,
> For[j = i, j < 18 + 1, j++,
> entMatr[[j, i]] = i
> ]
> ]
>
> (* initialize dOneCol *)
> dOneCol = Table[Subscript[n, x], {x, 171}];
>
> (* attempt to copy the values from entMatr to dOneCol *)
> q = 0;
> For[k = 1, k < 18 + 1, k++,
> For[p = k, p < 18 + 1, p++,
> dOneCol[[q]] = entMatr[[p,k]]
> q++
> ]
> ]
> dOneCol
> </pre>
Hello
You have to modify two things.
1. Missing semicolon
There is no semicolon between the command "dOneCol[[q]] =
entMatr[[p,k]]" and the command "q++". Therefore each entry of dOneCol
is multiplied by the actual value of q.
2. q starts at 0
This means that with your first assignment dOneCol[[0]] =
entMatr[[1,1]]" you modify the head of dOneCol. You can either set q=1
at the beginning or you can move q++ in front of the command
"dOneCol[[q]] = entMatr[[p, k]]". Both changes alone should work.
Finally. The following code should do what you want:
q = 1;
For[k = 1, k < 18 + 1, k++, For[p = k, p < 18 + 1, p++,
dOneCol[[q]] = entMatr[[p, k]]; q++]]
dOneCol
Best Regards
Norbert Marxer
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