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%% Polynomial Curve Fitting % This example shows how to fit a polynomial curve to a set of data using % |polyfit|. Use the |polyfit| function to find the coefficients of a % polynomial that fits a set of data in a least-squares sense using the % syntax % % p = polyfit(x,y,n), % % where: % % * |x| and |y| are vectors containing the |x| and |y| data to be fitted % * |n| is the degree of the polynomial to return % % Consider the _x-y_ test data % Copyright 2015 The MathWorks, Inc. x = [1 2 3 4 5]; y = [5.5 43.1 128 290.7 498.4]; %% % Use |polyfit| to find a third-degree polynomial that approximately fits % the data. p = polyfit(x,y,3) %% % After you obtain the polynomial using |polyfit|, use |polyval| to % evaluate the polynomial at other points that might not have been included % in the original data. % % Compute the values of the |polyfit| estimate over a finer domain 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