新手请教Matlab曲线拟合问题

[交通2部]

各位大侠：我算出了8个点数值，但是在进行曲线拟合时，老是弹出这样的错误：Warning: Polynomial is not unique; degree >= number of data points.
> In polyfit at 72
In Untitled at 61
??? Undefined function or method 'ployval' for input arguments of type 'double'.

Error in ==> Untitled at 62
Qs4=ployval(p,ua);
而我自己的相关程序如下：
ua=[ua41 ua42 ua43 ua44 ua45 ua46 ua47 ua48];
Qs=[Qs41 Qs42 Qs43 Qs44 Qs45 Qs46 Qs47 Qs48];
[p,s]=polyfit(ua,Qs,8);
Qs4=ployval(p,ua);
plot(ua,Qs4);
hold on;
plot(ua,Qs,‘b*’)
请问怎么处理啊？谢谢啦！:)