x=[-3:0.1:3];
y=0*x+1;
plot(x,f(x,y),'linewidth',2,'color','k');
axis([-3 3 -4 4]);
hold on
xlabel('X','fontweight','bold','fontsize',12);
ylabel('z','fontweight','bold','fontsize',12);
plot(1,0,'r+','linewidth',2)
text('string','g(x)=f(x,1)','position',[-2.5 3]);