spm_dcm_check_stability.m
31022b3a13e6master

spm_dcm_check_stability.m
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			function [is_stable,eigval] = spm_dcm_check_stability(DCM)
			% Check stability of a DCM using Lyapunov exponent
			% FORMAT [is_stable,eigval] = spm_dcm_check_stability(DCM)
			%
			% DCM - DCM structure or its filename
			%
			% is_stable - returns 1 if stable, 0 if not stable
			% eigval - Lyapunov exponent
			%
			% This function checks the stability of a DCM by examining the eigenvalue
			% spectrum for the the intrinsic connectivity matrix (Lyapunov exponent).
			%__________________________________________________________________________
			% Copyright (C) 2014 Wellcome Trust Centre for Neuroimaging

			% Will Penny & Klaas Enno Stephan & Peter Zeidman
			% $Id: spm_dcm_check_stability.m 6077 2014-06-30 16:55:03Z spm $


			%-Load DCM if necessary
			%--------------------------------------------------------------------------
			if ~isstruct(DCM)
			load(DCM);
			end

			%-Translate A-matrix to that used in spm_fx_fmri
			%--------------------------------------------------------------------------
			SE = diag(DCM.Ep.A);
			EE = DCM.Ep.A - diag(exp(SE)/2 + SE);

			%-Check stability
			%--------------------------------------------------------------------------
			eigval = max(eig(full(EE)));
			is_stable = eigval < 0;