Using QR Decomposition to find Eigenvalues values

[MarkRaz2]

Hi I'm trying to learn how to use QR Decomposition to find Eigenvalues values. The standard formula is A= QR
The way I understand it is that you obtain Q by using the Gram-Schmidt process to normalize A. I understand this process fine.

My question is how do you find R ? Is R just and upper triangular representation of A? if so what process/method is typically used to do this?

thanks

 

[blamocur]

Have you looked at https://en.wikipedia.org/wiki/QR_decomposition#Using_the_Gram–Schmidt_process ?

 

[Steven G]

If A=QR, then R = ???

 

[blamocur]

If A=QR, then R = ???

True, but the way [imath]R[/imath] is computed in the algorithm is, probably, more computationally efficient because it is assembled from the parts computed for [imath]Q[/imath].