Fit data to array values

I have a certain array of theoretical values which forms the y values of a graph. This graph is not analytic, so the theoretical array values are numerically generated. I want to see how good this theoretical array is to an actual data array. For eg, I have a theoretical array [1 1 1 1 1] which represents 5 points on a linspace(1,5). The data array is [0.987,0.95,1.06,1.02,1.04] over the same linspace. I want to see how good of a fit it is (calculate an R-squared value for the fit).

Answer 1

[KSSV]

x = 1:5 ;
y = [0.987,0.95,1.06,1.02,1.04] ;

p = polyfit(x,y,2) ;
yi = polyval(p,x) ;

figure
hold on
plot(x,y,'.r')
plot(x,yi)