function y=heavi(x)
% HEAVI -  Heaviside Function.
%
%          heavi(x) computes the Heaviside function of 
%          a scalar or matrix of real numbers x.
%
%              heavi(x) = 0 if x < 0
%              heavi(x) = 1 if x >= 0

% Created: 6/95 by R. Knobel

y = x>=0; 