How would one go about defining polynomials in MATLAB?

Question

Husnain Khalil 2018-2-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/384911-how-would-one-go-about-defining-polynomials-in-matlab

评论： Husnain Khalil 2018-2-26

1. Define P1=s^6+7s^5+2s4+9s^3+10s^2+12^s+15,

P2=s^6+9s^5+8s^4+9s^3+12s^2+15s+20

I have tried to create a row matrix and use polyval but because s is an undefined value I'm unsure how to proceed from there.

2 个评论
显示无隐藏无

Torsten 2018-2-26

No s needed.

Take a look at the example under

https://de.mathworks.com/help/matlab/ref/polyval.html

Best wishes

Torsten.

Husnain Khalil 2018-2-26

Hi Torsten,

Thanks for replying but I'm still unsure how it would work. If I put my code as:

p1=[1 7 2 9 10 12 15] then try and use poly, it does not work.

nor does: poly([1 [6]], [7 [5]], [2 [4]], [9 [3]], [10 [2]], [12 [1]], [15 [0]],[s])

could you provide any further clarification?

Regards,

Husnain Khalil

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Image Analyst 2018-2-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/384911-how-would-one-go-about-defining-polynomials-in-matlab#answer_307192

在 MATLAB Online 中打开

Try this:

s = linspace(-1, 1, 500);
P1=s.^6+...
  7 * s .^ 5+...
  2 * s .^ 4+...
  9 * s .^ 3+...
  10 * s .^ 2+...
  12 * s + 15;
plot(s, P1, 'b-', 'LineWidth', 2);
grid on;
P2=s .^ 6 + ...
  9 * s .^ 5 + ...
  8 * s .^ 4 + ...
  9 * s .^ 3 + ...
  12 * s .^ 2 + ...
  15 * s + 20;
hold on;
plot(s, P2, 'r-', 'LineWidth', 2);
legend('P1', 'P2');

2 个评论
显示无隐藏无

Image Analyst 2018-2-26

编辑：Image Analyst 2018-2-26

在 MATLAB Online 中打开

Or this:

s = linspace(-1, 1, 500);
coefficients1=[1 7 2 9 10 12 15] 
P1 = polyval(coefficients1, s);
plot(s, P1, 'b-', 'LineWidth', 2);
grid on;
coefficients2 = [1 9 8 9 12 15 20] 
P2 = polyval(coefficients2, s);
hold on;
plot(s, P2, 'r-', 'LineWidth', 2);
legend('P1', 'P2');