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Scilab manual >> Linear Algebra > 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This function is obsolete and is now included in the schur function.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
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

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Last updated:
Wed Jan 26 16:23:41 CET 2011