Scilab Function

gschur - generalized Schur form (obsolete).

Calling Sequence

[As,Es]=gschur(A,E)
[As,Es,Q,Z]=gschur(A,E)
[As,Es,Z,dim] = gschur(A,E,flag)
[As,Es,Z,dim]= gschur(A,E,extern)

Parameters

Description

This function is obsolete and is now included in the schur function. In most cases the gschur function will still work as before, but it will be removed in the future release.

The first three syntaxes can be replaced by 

[As,Es]=schur(A,E)
[As,Es,Q,Z]=schur(A,E);Q=Q' //NOTE THE TRANPOSITION HERE
[As,Es,Z,dim] = schur(A,E,flag)

The last syntax requires little more adaptations:

  • if extern is a scilab function the new calling sequence should be [As,Es,Z,dim]= schur(A,E,Nextern) with Nextern defined as follow: 
    • function t=Nextern(R)
if R(2)==0 then
  t=extern([1,R(1),R(3)])==1
else
  c=(R(1)+%i*R(2))/R(3)
  t=extern([2,real(c+c'),real(c*c')])==1
end
endfunction
  • if extern is the name of an external function coded in Fortran or C the new calling sequence should be [As,Es,Z,dim]= schur(A,E,'nextern') with nextern defined as follow: 
    •       logical function nextern(ar,ai,beta)
      double precision ar,ai,beta
      integer r,extern
      if (ai.eq.0.0d0) then
        r=extern(1,ar,beta,0.0d0,0.0d0)
      else
        r=extern(2,0.0d0,0.0d0,2.0d0*ar,ar*ar+ai*ai)
      endif
      nextern=r.eq.1
      end

    See Also