中文说明：本人用matlab编写的rels(最小二乘法），rls(递推增广最小二乘法)，riv(辅助变量法递推算法)的程序，都是2阶的，稍改动就可以变成其它阶次
English Description：
I use matlab to write the program of rels (least square method), RLS (recursive extended least square method), riv (auxiliary variable method, recursive calculation method), all of which are of order 2, and can be changed into other orders with a little change