Second order regression

clear all;
close all;

x = [-3 -1 1 3];
y = [1.3 1.5 1.4 1.2];

G = ones(length(x),3);
G(:,2) = x';
G(:,3) = x'.^2;

beta = (G'*G)\G'*y';
A = beta(1);
B = beta(2);
C = beta(3);

scatter(x,y,'filled')
hold on
x = linspace(-3,3);
plot(x,A + B*x + C*x.^2)

Figure: