Mercurial > octave-nkf
view scripts/control/lyap.m @ 73:f3c9042fd609
[project @ 1993-08-30 14:49:08 by jwe]
author | jwe |
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date | Mon, 30 Aug 1993 14:54:55 +0000 |
parents | 8d4431f4a00a |
children | 16a24e76d6e0 |
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function x = lyap (a, b, c) # Usage: x = lyap (a, b {,c}) # # If (a, b, c) are specified, then lyap returns the solution of the # Sylvester equation # # a x + x b + c = 0 # # If only (a, b) are specified, then lyap returns the solution of the # Lyapunov equation # # a' x + x a + b = 0 # # If b is not square, then lyap returns the solution of either # # a' x + x a + b' b = 0 # # or # # a x + x a' + b b' = 0 # # whichever is appropriate. # # Solves by using the Bartels-Stewart algorithm (1972). # Written by A. S. Hodel (scotte@eng.auburn.edu) August 1993. if (nargin != 3 && nargin != 2) error ("usage: lyap (a, b {,c})"); endif if ((n = is_square(a)) == 0) error ("lyap: a is not square"); endif if (nargin == 2) # Transform Lyapunov equation to Sylvester equation form. if ((m = is_square (b)) == 0) if ((m = rows (b)) == n) # solve a x + x a' + b b' = 0 b = b * b'; a = a'; else # Try to solve a'x + x a + b' b = 0. m = columns (b); b = b' * b; endif if (m != n) error ("lyap: a, b not conformably dimensioned"); endif endif # Set up Sylvester equation. c = b; b = a; a = b' else # Check dimensions. if ((m = is_square (b)) == 0) error ("lyap: b must be square in a sylvester equation"); endif [n1, m1] = size(c); if (n != n1 || m != m1) error("lyap: a,b,c not conformably dimensioned"); endif; endif # Call octave built-in function. x = syl (a, b, c); endfunction