Make a triangular matrix from a square matrix

[quin]

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 alot

 

[jfgobin]

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.

 

[quin]

matlab and mathematica couldn't do it.matrix is very complex for these softwares and they cannot calculate eigenvalues of matrix

 

[NemoReally]

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?

 

[quin]

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 alot

 

[DuncanM]

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.