MATLAB: How to fit a curve to 3 points automatically

curve fitting

Guys, I'd like to find an automatic method for fitting y=-x^2 curve to three points x=[12 67 16]; can any one suggest me a matlab code please?

Best Answer

Maybe something like
A=[x1^2 x1 1
   x2^2 x2 1
   x3^2 x3 1];
rhs=[y1 ; y2 ; y3];
sol=A\b;
func=@(x)sol(1)*x.^2+sol(2)*x+sol(3);
x=x1:0.1:x2;
y=func(x);
plot(x,y)
where (x1,y1), (x2,y2), (x3,y3) are the points in question ?
Best wishes
Torsten.
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