﻿功能:多项式拟合

格式:
[a,error] = PolyFit(x,y,n)
[a,error] = PolyFit(x,y)
 
x:矩阵变量存储的自变量数据
y:与x同维数的因变量矩阵数据
n:一个拟合的最高次数,默认为2

a:返回的多项式系数,本函数主要是要拟合 
$$y = a_0 + \sum_{i=1}^na_ix^i$$这么一类问题.其中返回值 a = [a0,a1,a2,……,an]
error:返回拟合的残差平方和

例子:
x = [ 1.00000000000000    2.00000000000000    3.00000000000000    4.00000000000000    5.00000000000000    6.00000000000000    7.00000000000000    8.00000000000000    9.00000000000000    10.0000000000000 ];
y = [ 9.00000000000000    31.0000000000000    83.0000000000000    177.000000000000    325.000000000000    539.000000000000    831.000000000000    1213.00000000000    1697.00000000000    2295.00000000000 ];
[an,er] = PolyFit(x,y,3)//回车得到如下结果
an =
[ 5.00000000000000   -1.00000000000000    3.00000000000000    2.00000000000000 ]
er =
[ 0.00000000000000 ]


y1 = {PolyValue<矩阵运算/PolyValue>}(an, x)//可以执行本命令查看拟合预测值