Math 171 - Alexiades
HW: Polynomial fitting to data
Consider some data points, e.g.
x = [0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0];
y = [0.01 0.1 0.3 0.5 0.5 0.6 0.6 0.3 0.1 0.3 0.04];
Fit a quadratic, find the LSerror, and plot:
P2 = polyfit(x,y,2); %% (coefficients of) 2nd degree polynomial best fitting the data
y2 = polyval(P2, x); %% evaluate P2 at x-values
E2 = sum( (y-y2).^2 ) %% LS error
plot(x,y,'ko', x, y2, 'r-*' )
Similarly, fit a 4th degree polynomial, find E4, and plot
Similarly, fit a 10th degree polynomial, find E10, and plot
With 11 points, P10 is the highest degree that can be found
and it interpolates the data (passes through the points).