Polynomial Curve Fitting

For my introductory MATLAB programming class, I need to create a function that fits an n'th order polynomial curve to given data using least squares method.

[fx,a] = curvepoly (x,y,n)

fx=y-axis values on the curve-fit corresponding to the cc-values

a=the polynomial coefficients found

x=[-4. -3.5 -3. -2.5 -2. -1.5 -1. -0.5 0. 0.5 1. 1.5 2. 2.5]

y=[0.0013 0.0026 0.0052 0.0106 0.0213 0.0429 0.0863 0.1739 0.35 0.7048 1.4193 2.8582 5.7556 11.5904]

n=order of polynomial desired

Please use the most basic syntax possible Thanks

Answer 1

[Walter Roberson]

One "most basic syntax" function coming up:

function [fx,a]=curvefit(x,y,n)
a=polyfit(x,y,n)
fx=polyval(a,x)

[Stephen Shortridge]

I wish I could use that but I need to write a code that does what polyfit does.

[Walter Roberson]

function [fx,a]=curvefit(x,y,n)

x=x(:);

for K=0:n-1

b(:,n-K)=x.^K;

end

a=b\y;

fx=polyval(a,x);