How to Multiplying matrices

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?

Answer 1

[David Hill]

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;

[Yanuar Rizki Pahlevi]

is there a way so the B matrix is automatically fill with x^0:x^n-1?

[David Hill]

a=5:-1:1;
syms x;
b=sum(a.*(repmat([x],1,length(a)).^(0:4)));

[Yanuar Rizki Pahlevi]

thank you for your help!

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

[David Hill]

Yes

Answer 2

[Yanuar Rizki Pahlevi]

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?

[David Hill]

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]

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