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Best answer by Werner_E

Just the determinant?

So how about a small modification in Alvaro's RREF?

Werner_E_0-1680316267529.png

Sure could be done more efficient, but for a quick hack it seems to work OK. No error  check (matrix square, etc.) is done. I simply changed the program to return 0 if no suitable pivot element could be found.

It also works symbolically, at least as long as only numbers are used. It fails symbolically when variables are used because the if-conditions can't be evaluated symbolically without knowing their actual values.

 

2 replies

ttokoro
21-Topaz I
ttokoro21-Topaz I
21-Topaz I
March 30, 2023

Your code is ok. But your data A is not able to make A^-1 because the 0 0 3 9 and 0 0 5 15 are same.

ttokoro_0-1680219369354.png

 

 


image.pngimage.pngimage.pngimage.pngimage.png

t.t.
    L
    lvl10720-TurquoiseAuthor
    20-Turquoise
    March 31, 2023

    Many thanks for your response, Ttokoro. My Mathcad 15 with your code is the following :

    I.PNG

     

                                                        ___

     

    II.PNG

      

         But I still got stuck to keep going to write a code for symbolic evaluate a DETERMINANT of a matrix above. My question is "How to write a code for SYMBOLIC evaluate a DETERMINANT of a matrix and with a Gauss-Jordan method or any other idea."

        Best Regards.

             Loi.

    L
    lvl10720-TurquoiseAuthor
    20-Turquoise
    March 31, 2023

       And a similar code using Gauss-Jordan method, in the forum, is :

     

    III.png

     

     

      But I would like to have a symbolic evaluate result is : ==> 0

    W
    Werner_E25-Diamond IAnswer
    25-Diamond I
    April 1, 2023

    Just the determinant?

    So how about a small modification in Alvaro's RREF?

    Werner_E_0-1680316267529.png

    Sure could be done more efficient, but for a quick hack it seems to work OK. No error  check (matrix square, etc.) is done. I simply changed the program to return 0 if no suitable pivot element could be found.

    It also works symbolically, at least as long as only numbers are used. It fails symbolically when variables are used because the if-conditions can't be evaluated symbolically without knowing their actual values.

     

      L
      lvl10720-TurquoiseAuthor
      20-Turquoise
      April 1, 2023

      2.png

       

         I really appreciate your time and help, Werner. ðŸ˜Š ðŸ¤” ðŸ™„ especially your explanation. 

      And I guess now it's time keep going with Alvaro's RREF and modify his CODE for inverse of a square matrix. ( I guess I would still be helped more ... ).

       Thanks again,

          Best Regards.

              Loi. 

      L
      lvl10720-TurquoiseAuthor
      20-Turquoise
      April 1, 2023

      A small modification in Tom Gutman's det( ) ?

       

      3.png

       

      for symbolic evaluate result.

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