id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
3510	Introduce new diag function for creating diagonal matrices and for returning the diagonal of a matrix	marco.guazzone@…	Gunter	"Introduce a new '''diag''' free function in the spirit of the MATLAB's ''diag'' function and Mathematica's ''DiagonalMatrix function''.

Basically it allows both the creation of a ''generalized'' diagonal matrix and the creation of a ''diagonal'' view of an existing matrix.

A ''generalized'' k-th diagonal matrix is a special kind of matrix which has all elements set to zero but the ones on its k-th diagonal. The integer k is the offset from the main diagonal, that is:

* k = 0: the elements on the main diagonal can be different from zero.

* k > 0: only the elements on the k-th upper diagonal can be different from zero.

* k < 0: only the elements on the k-th lower diagonal can be different from zero.

A generalized diagonal matrix can be a rectangular matrix.



Here below is a list of the requested cases:

* Create a square diagonal matrix M with vector V
being the k-th diagonal
  {{{M = diag(v,k)}}}

* Like the above, but M has layout l (e.g., column major)
  {{{M = diag(v,k,l)}}}

* Create a rectangular diagonal matrix M of size mXn with vector V being the k-th diagonal
  {{{M = diag(v,m,n,k)}}}


* Like the above, but M has layout l (e.g., column major)
  {{{M = diag(v,m,n,k,l)}}}

* Create a diagonal view of the k-th diagonal of matrix M
  {{{v = diag(M,k)}}}
"	Feature Requests	new	Boost 1.41.0	uBLAS	Boost 1.40.0	Not Applicable