Compute polynomial coefficient with unequal vector?

2 次查看（过去 30 天）

AniCnx 2017-10-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/361672-compute-polynomial-coefficient-with-unequal-vector

评论： AniCnx 2017-10-17

Hello all, I have question about to compute polynomial coefficient with unequal number of membership of 2 vectors. If I have vector A as 10x1 and vector B as 7x1, can I possibly compute coefficient with order 4 of this 2 vectors? Thanks Ani.

2 个评论
显示无隐藏无

KSSV 2017-10-17

A fourth order polynomial has five unknowns..you have seven points known..you should be able to do it eh.

AniCnx 2017-10-17

On polyfit of matlab, it needs equally membership of vector A and B. Do it has any built in function of that problem?

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

KSSV 2017-10-17

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/361672-compute-polynomial-coefficient-with-unequal-vector#answer_286140

在 MATLAB Online 中打开

%%a random data
x = rand(10,1) ;
y = rand(7,1) ;
% sort x in ascending order and pick first seven 
x = x(1:7) ;
%
[x,idx] = sort(x) ;
y = y(idx) ;
%%fit fourth order polymomial
[P,S] = polyfit(x,y,4) ;
x1 = linspace(min(x),max(x));
y1 = polyval(P,x1);
figure
plot(x,y,'-or')
hold on
plot(x1,y1)
hold off

3 个评论
显示 1更早的评论隐藏 1更早的评论

KSSV 2017-10-17

Yes...

AniCnx 2017-10-17

Thank you very much, KSSV. May I ask one more question? That I have A=10x1, B=7x1. If I re-sampling B to be C=10x1. Coefficient of AB is equal or not equal to AC?

请先登录，再进行评论。