Extracting points representing curve

I have certain set of (x,y) coordinates representing a shape. How to extract those points which define a curve among the available points?

[KSSV]

Already you have the points (x,y) in hand. What you want?

[Shweta Saboo]

I want to select(extract) only those points representing curve from the complete set of points.

[KSSV]

Okay share the data and what you expect.

Answer 1

[KSSV]

In case are you looking for polyfit. ? Let (x,y) be the points you have and you want fit a quadratic polynomial.

p = polyfit(x,y,2) ; 
xi = x ; 
yi = polyval(p,xi) ;
iwant = [xi yi] ; % assuming xi, yi to be column arrays