Syntax

Description

[US,TS] = ordschur(U,T,select)reorders the Schur factorizationX = U*T*U'produced by theschurfunction and returns the reordered Schur matrixTSand the cumulative orthogonal transformationUSsuch thatX = US*TS*US'. In this reordering, the selected cluster of eigenvalues appears in the leading (upper left) diagonal blocks of the quasitriangular Schur matrixTS, and the corresponding invariant subspace is spanned by the leading columns ofUS. The logical vectorselectspecifies the selected cluster asE(select)whereEis the vector of eigenvalues as they appear alongT's diagonal.

NoteTo extractEfromT, useE = ordeig(T), instead ofeig. This ensures that the eigenvalues inEoccur in the same order as they appear on the diagonal ofTS.

[US,TS] = ordschur(U,T,keyword)sets the selected cluster to include all eigenvalues in one of the following regions:

[US,TS] = ordschur(U,T,clusters)reorders multiple clusters at once. Given a vectorclustersof cluster indices, commensurate withE = ordeig(T), and such that all eigenvalues with the sameclustersvalue form one cluster,ordschursorts the specified clusters in descending order along the diagonal ofTS, the cluster with highest index appearing in the upper left corner.

See Also

ordeig|ordqz|schur