Polynomial Curve Fitting
polyfit finds the coefficients of a polynomial that fits a set of data in a least-squares sense:p = polyfit(x,y,n)


x and y are vectors containing the x and y data to be fitted, and n is the degree of the polynomial to return. For example, consider the x-y test datax = [1 2 3 4 5]; y = [5.5 43.1 128 290.7 498.4];


A third degree polynomial that approximately fits the data isp = polyfit(x,y,3)
p = -0.1917 31.5821 -60.3262 35.3400


Compute the values of the polyfit estimate over a finer range, and plot the estimate over the real data values for comparison:x2 = 1:.1:5; y2 = polyval(p,x2); plot(x,y,'o',x2,y2) grid on