gschur

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)  

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This function is obsolete and is now included in the schur function.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
   
        
ifextern 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

external, schur