t=-pi:0.3:pi; y=1./(1+exp(-t));
subplot(221), plot(t,y); title('plot(t,y)')
subplot(222), stem(t,y); title('stem(t,y)')
subplot(223), semilogy(t,y); title('semilogy(t,y)')
subplot(224), stairs(t,y); title('stairs(t,y)')