Lagrange interpolation

Syntax: vout = INTERPOLATE(x,y,xout,'LAGRANGE')

If the LAGRANGE keyword is used, the interpolating method used is general Lagrange interpolation. The degree of the interpolating polynomial depends on the number of input data points.

Suppose that N is the number of points, equal to the lengths of x and y. If N = 2, then a simple straight line is used for interpolating. If N = 3 or N = 4, then a quadratic is used. If N ≥ 5, then a polynomial of degree 4 is used for the interpolation.

  Spline interpolation
  Fritch-Carlson interpolation