请教绘图问题

[kayneo]

作者: cfchenchen

这是画的图:
x=linspace(-0.5,110,100);
y1 =(3*x.^2+1)./(x.^3+x+3);
y2 =6*x./(x.^3+x+3)-(3*x.^2+1).^2./(x.^3+x+3).^2;
subplot(2,2,1);plot(x,y1);title('一阶微分图形');
subplot(2,2,2);plot(x,y2);title('二阶微分图形');
subplot(2,2,3);plot(x,y1,x,y2);title('一阶与二阶微分混合图形');

经过前面之后，后面的这样比较好：
a=linspace(-0.5,110,100);
y1=subs(y1,x,a);
y2=subs(y2,x,a);

subplot(2,2,1);plot(a,y1);title('一阶微分图形');
subplot(2,2,2);plot(a,y2);title('二阶微分图形');
subplot(2,2,3);plot(a',[y1',y2']);title('一阶与二阶微分混合图形');;title('一阶与二阶微分混合图形');