##### 22.6.2.6 etree

— Loadable Function: p = etree (s)
— Loadable Function: p = etree (s, typ)
— Loadable Function: [p, q] = etree (s, typ)

> Returns the elimination tree for the matrix s. By default s is assumed to be symmetric and the symmetric elimination tree is returned. The argument typ controls whether a symmetric or column elimination tree is returned. Valid values of typ are 'sym' or 'col', for symmetric or column elimination tree respectively

> Called with a second argument, etree also returns the postorder permutations on the tree.