function [y] = tfun(x,alpha)
%  Find t(x,alpha), for a column vector x

n=length(x);
y =zeros(n,1);
for i=1:n
	if(x(i)>0.0)
		tmp=1.0/(1+exp(-alpha*x(i)));
		y(i)=alpha*tmp*(1-tmp);
	else
		tmp=exp(alpha*x(i))/(1+exp(alpha*x(i)));
		y(i)=alpha*tmp*(1-tmp);
	end;
end;

return;
