%The phase error for Runge_Kutta 1 is given by 
%
%erp=1-arctan(wh)/wh
wh1=(-100:0.01:100);
erp1=1-atan(wh1)./wh1;

%The phase error for Runge-Kutta 2 is given by 

%erp2=1-(1./wh)*atan((wh./(1-(wh)^2/2)));
wh2=(-4:0.001:4);
erp2=1-atan(wh2./(1-((wh2).^2)/2))./wh2;

subplot(2,1,1);
plot(wh1,erp1);
xlabel('wh');ylabel('Phase Error');

subplot(2,1,2);
plot(wh2,erp2);
xlabel('wh');ylabel('Phase Error');