function res = phi1(x)
for k = 1:length(x)
	if x(k) >= 0 & x(k) <= 2;
		res(k) = phi(x(k));
    elseif x(k) <= 0;
    		res(k) = phi1(-x(k));
        else
            res(k) = -phi1(4-x(k));
	end
end