Fitting a linear sine curve with polynomial curve

I don't have any data points. I have seen your past answers of fitting the sinusoidal function using pure Matlab functions. But those coefficients is for non-linear sinusoidal function. Can you assist me in fitting a linear sine curve between o and 2pi with the polynomial curve of power 4? I am a noobie at Matlab coding. Kindly assist for the same.

[Torsten]

What sine-curve s(x) do you have in mind ?

s(x) = ?

[Abi sek]

Hi Torsten, just we can proceed with s(x) =sin(x)

Answer 1

[Torsten]

x=linspace(0,2*pi,100);
x=transpose(x);
A=[ones(numel(x),1),x,x.^2,x.^3,x.^4];
b=sin(x);
sol=A\b;  % Polynomial is given by sol(1)+sol(2)*x+sol(3)*x^2+sol(4)*x^3+sol(5)*x^4

Best wishes

Torsten.

[Abi sek]

Thanks Torsten

[Abi sek]

how to plot an original sine curve with the fitted polynomial curve; and also curve of the difference between the two?

[Torsten]

polynomial=sol(1)+sol(2)*x+sol(3)*x.^2+sol(4)*x.^3+sol(5)*x.^4;
plot(x,sin(x),x,polynomial,x,sin(x)-polynomial)

[Abi sek]

Thank you