stable regression doesnt work right. ST > 0 is not true

dmd.m

@@ -70,7 +70,8 @@ classdef dmd < handle
 		end
 		
 		function stableRegression(obj,varargin) % argument is truncation rank r
-			% Follows Ian Manchester's not-yet published work on stable
+			warning('stableRegression() doesn''t work - something is wrong.');
+			% Follows Ian Manchester's not-yet-published work on stable
 			% least squares
             if nargin == 2
                 obj.r = varargin{1};
@@ -100,6 +101,10 @@ classdef dmd < handle
 			Sigma_zz = ztilde*ztilde'/N;
 			Sigma_s = (Sigma_xx + Sigma_zz)/2;
 			
+			ST = [Sigma_xx, Sigma_zx;
+				Sigma_zx', Sigma_zz];
+
+			disp(eig(ST));
 		
 			obj.Atilde = Sigma_zx/Sigma_s;
             [obj.W,obj.Lambda] = eig(obj.Atilde);

examples/dmd_vortex.m

@@ -13,7 +13,9 @@ vortex_dmd = dmd(VORTALL,verbose);
 
 % Step 2: perform DMD regression on data
 truncation_rank = 21; % rank to truncate reduced dynamics to
-vortex_dmd.regression(truncation_rank);
+% vortex_dmd.regression(truncation_rank);
+vortex_dmd.stableRegression(truncation_rank);
+disp(max(abs(eig(vortex_dmd.Atilde))));
 
 % Step 3: reconstruct VORTALL(:,2:end) using DMD approximation
 X2hat = vortex_dmd.reconstruct(); % not used in the script