MATLAB: Matlab code for this type of factorization.A has a SR decomposition A = SR , where S ∈ R^ 2n ×2n is a symplectic matrix, i.e. S ^TJS = J

controlmatrix decomposition

J=[0 -I;I 0] where I∈R^ n ×n means identity matrix. R=[R11 R12;R21 R22]∈ R^ 2n ×2n , is constituted by upper triangular matrices R11 , R12 , R22 and strictly upper triangular matrix R21. diag (R11 ) =|diag (R22 )| and diag (R12 ) = 0 , then the SR decomposition is unique.

Best Answer

I'm not very acquainted with the SR decomposition (all I know about it I found just now by googling). I would suggest to take a look at what seems to be the original paper, "Matrix factorizations for symplectic QR-like methods" by Bunse-Gerstner. This seems to suggest an algorithm using other factorizations (e.g. QR) as building blocks.
I'm also tagging this Control, because it seems that this decomposition has applications in total control.