Make a triangular matrix from a square matrix

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Discussion Overview

The discussion revolves around the challenge of finding eigenvalues of a complex 12x12 matrix, with a focus on transforming the matrix into an upper triangular form. Participants explore methods and tools, particularly MATLAB and Mathematica, to achieve this transformation and compute eigenvalues.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses difficulty in finding eigenvalues of a complicated 12x12 matrix and seeks guidance on how to convert it to upper triangular form using MATLAB or Mathematica.
  • Another participant suggests using built-in functions for eigenvalues instead of transforming the matrix, questioning the necessity of diagonalization.
  • A participant claims that MATLAB and Mathematica are unable to handle the complexity of the matrix for eigenvalue calculations.
  • QR decomposition is proposed as a method for obtaining an upper triangular matrix, with references to relevant functions in both MATLAB and Mathematica.
  • One participant clarifies that their matrix is symbolic, indicating that QR decomposition may not be suitable for their needs.
  • A later reply expresses skepticism about obtaining symbolic solutions for the eigenvalues of a 12x12 matrix, suggesting that the complexity increases significantly compared to smaller matrices.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to take. There are competing views on whether to transform the matrix or directly compute eigenvalues, and uncertainty remains regarding the capabilities of the software for symbolic matrices.

Contextual Notes

Limitations include the complexity of the matrix and the potential inadequacy of software tools for symbolic computation. Participants note that methods like QR decomposition may not apply to symbolic matrices.

quin
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dear users
I have a problem in finding eigenvalues of a 12*12 because the 12*12 matrix is so complicated
so i decided to first make my 12*12 matrix in form of upper triangular form but I don't know how can I do it with MATLAB or mathematica?
can you please tell me that what is the formula in MATLAB or mathematica for make an upper triangular matrix from my own 12*12 matrix?

thanks a lot
 
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Hello,

If you need to get the eigenvalues/eigenvectors, why don't you use the corresponding function, instead making the matrix diagonal?

Just thinking ...

J.
 
matlab and mathematica couldn't do it.matrix is very complex for these softwares and they cannot calculate eigenvalues of matrix
 
NemoReally said:
QR decomposition. http://en.wikipedia.org/wiki/QR_decomposition

Look up the function qr in Matlab and QRDecomposition in Mathematica. Is your matrix too complicated to post? Is it numeric or symbolic?

thank you for your guide but my matrix which I want to find its eigenvalue is symbolic and qr is for numeric matrix.

these are mathematica's and matlab's files of my matrix so that you can have a look on it.
thank you a lot
 

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You want the symbolic solution for the eigenvalues of a 12x12 matrix?!

That would be a nightmare!

As far as I know, the various methods of computing eigenvalues--QR Decomposition, Characteristic Polynomial, etc.--are all pretty complicated. Perhaps the solutions of a 3x3 matrix would be nice concise answers. However, the solutions of a 12x12 matrix sure would not be.
 

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