How to Multiplying matrices

Question

Yanuar Rizki Pahlevi 2020-9-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/589516-how-to-multiplying-matrices

评论： David Hill 2020-9-6

采纳的回答： David Hill

Hi, i need help.

how can I multplying matrices 1x3 with 3x1 with variable only for it element.

as example, I want to multiply [1 2 3 4 5] with [x^0 x^n-4 x^n-3 x^n-2 x^n-1]

I have done it with fliplr and poly2sym, but, is there any way without using poly2sym at all?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

David Hill 2020-9-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/589516-how-to-multiplying-matrices#answer_490411

在 MATLAB Online 中打开

syms x n;
a=[1,2,3,4,5];
b=[x; x^n-4; x^n-3; x^n-2; x^n-1];
c=a*b;

4 个评论
显示 2更早的评论隐藏 2更早的评论

Yanuar Rizki Pahlevi 2020-9-6

thank you for your help!

I am asking your permission to update a little so it works on my function.

David Hill 2020-9-6

Yes

请先登录，再进行评论。

Answer 2

Yanuar Rizki Pahlevi 2020-9-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/589516-how-to-multiplying-matrices#answer_490414

Okay, I think I have misleading with the question, what I am trying to do is to create a function which result is an equation. if input isA= [5 4 3 2 1], then the result is 5+4x^2+3x^3+2x^4+x^5. first thing that came to my mind is, to create a matrix multiplying, A and its x matrix. am I on the right way?

2 个评论
显示无隐藏无

David Hill 2020-9-5

You must mean 5+4*x+3*x^2+2*x^3+x^4. Why not just use charateristic polynomial functions?

https://www.mathworks.com/help/matlab/math/create-and-evaluate-polynomials.html?s_tid=srchtitle

Yanuar Rizki Pahlevi 2020-9-5

Oh, yes sorry I mistyped that. Yes, I can perform it using characteristic polynomial function and with help of fliplr.

But, I am trying not use any built in polynomial at all..

I have trying using FOR loops, but the result is not what I meant to be. the result is 15+15x+15x2+15x3+15x4. it is wrong but it feels I am close to my goal

请先登录，再进行评论。