function y = modsig(x, parameter)%SIG_MF	Sigmoidal membership function with two parameters.%	SIG_MF(x, [a, c]) returns a matrix y with the same size%	as x; each element of y is a grade of membership.%	Jyh-Shing Roger Jang, 6-29-93.%% a = parameter(1); c = parameter(2);y = 1./(1 + exp(-x));