What is a Quasi Upper Triangular Matrix?

[jezza10181]

Hi, I am dealing with a 'quasi upper triangular matrix', that is mentioned in the book 'Matrix Computations' by Golub & Van Loan. However, neither in the book itself, or anywhere on the internet, am I able to find a formal definition of a 'quasi upper triangular matrix'.

I have a rough idea what this is.. an upper triangular matrix, with the odd non-zero element(s), somewhere along it's sub-diagonal. But I need an actual formal definition. Anyone furnish me with one please?

 

[AlephZero]

I have a rough idea what this is.. an upper triangular matrix, with the odd non-zero element(s), somewhere along it's sub-diagonal. But I need an actual formal definition. Anyone furnish me with one please?

You probably mean "a block upper triangular matrix with either 1x1 or 2x2 blocks on the diagonal."

http://books.google.co.uk/books?id=...epage&q=quasi upper triangular matrix&f=false

http://reference.wolfram.com/legacy.../AdvancedDocumentationLinearAlgebra3.4.5.html

It should be clear exactly what G&VL mean from the context in the book.

 

[jezza10181]

Thanks, the first link was very helpful