x1=-1:.1:0
x2=0:.1:3;
x3=3:.1:3.5;
h1=cos(x1);
h2=exp(x2);
h3=x3.^3+exp(3)-9;
x=[x1,x2,x3];
h=[h1,h2,h3];
plot(x,h)
x的范围你自己调整