MATLAB画出多项式曲线不平滑怎么改进？

Question

x=[0:5:30];
p=[0.00,0.058,-2.094,33.88,-246.6,688,-181.0];
y=polyval(p,x);
plot(x,y,'r')

Answer 1

x=0:5:30;
y=[0.00,0.058,-2.094,33.88,-246.6,688,-181.0];
p=ployfit(x,y,2); % 2表示二阶拟合，阶数越高，曲线越理想
disp('二阶拟合'),f=poly2str(p,'x'); % f表示拟合的二阶函数

x1=0:2:30; %缩小取值间隔
y1=polyval(p,x1); %polyval多项式函数p在x1处的值
plot(x1,y1,'r-')