equation solving – Duplicate RowReduce function


AA = {{a, b, c, d}, {e, f, g, h}, {i, j, k, l}};
AAold = AA;
nn = Length[AA];
For[ii = 1, ii <= nn, ii++,
    If[Quiet[IntegerQ[AA[[ii, ii]]^0]] == False,
       kk = ii + 1;
       While[kk < nn && Quiet[IntegerQ[AA[[kk, ii]]^0]] == False,
             kk = kk + 1
       If[kk > nn,
          Print["Singular matrix"];
       For[jj = 1, jj <= nn + 1, jj++,
           ll = AA[[ii, jj]];
           AA[[ii, jj]] = AA[[kk, jj]];
           AA[[kk, jj]] = ll
    For[jj = 1, jj <= nn, jj++,
        If[ii != jj,
           ll = AA[[jj, ii]]/AA[[ii, ii]];
           For[kk = 1, kk <= nn + 1, kk++,
               AA[[jj, kk]] = AA[[jj, kk]] - AA[[ii, kk]] ll
For[ii = 1, ii <= nn, ii++,
    AA[[ii, nn + 1]] = AA[[ii, nn + 1]]/AA[[ii, ii]];
    AA[[ii, ii]] = 1
FullSimplify[AA == RowReduce[AAold]]

I get


and the same if I define:

AA = {{0, b, c, d}, {e, f, g, h}, {i, j, k, l}};


AA = {{0, b, c, d}, {0, f, g, h}, {i, j, k, l}};

On the other hand, if I define:

AA = {{0, b, c, d}, {0, f, g, h}, {0, j, k, l}};

I would expect as output:

Singular matrix

when I get error messages instead. Could anyone kindly tell me how to fix this code without twisting it?


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y u no do it?

Advertise virtually anything here, with CPM banner ads, CPM email ads and CPC contextual links. You can target relevant areas of the site and show ads based on geographical location of the user if you wish.

Starts at just $1 per CPM or $0.10 per CPC.

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I need a little help please.
I’m using SharePoint 2013, with no SharePoint designer (disabled by the administrator).
I have a list, in which a have duplicated entries in a column named Title. I need to count those duplicates so I can apply a filter and view just those who have 3 or more occurrences. is it possible?

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I have an Excel file that contains the data of a website’s users. In column A I have their username, and in column B I have their email address. Unfortunately, there are many duplicates: both inside the same column, and across.


  1. Thelegend28 | myemail@gmail.com
  2. timmyhs | timmysdademail@gmail.com
  3. l33tu53r | iml33t@live.com
  4. Thelegend28 | duplicatemail@hotmail.com
  5. 2l33t4u | iml33t@live.com
  6. timmyhs | timmysdademail@gmail.com

As you can see, not only do I have users that are registered twice with the same username and email (2. and 6.), but I also sometimes have different unique usernames linked to the same email (3. and 5.) and usernames that are linked to more than one address (1. and 4.).

What I need to do, if possible, is format these three occurrences differently.

Of course, any help is greatly appreciated. I’m just a noob, but I’m trying to learn. Thank you all in advance.

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