Cubic splines for gnuplot

Library to create cubic hermite splines in gnuplot. Cubic splines are C1 piece-wise polynomial functions (of local degree 3) for which are specified value and first-derivative of the control points.

I used this library to create sketches of second-order [Lagrangian structure functions for turbulence (e.g. Fig.3 in this paper) as in the example above.

Usage

load "cubic_hermite_spline.lib.gnu"
set parametric
plot t, cubHerMulti5t(x0,u0, x1,u1, x2,u2, x3,u3, x4,u4, x5,u5 ,t)

Here xi,ui are, respectively, the value of the spline and of its first derivative.

The functions cubHerMulti2t, …, cubHerMulti5t expect, respectively, 2, … , 5 input control points.

TODO

The library can be easily extended to more control points; the API as well should be modified to accept arrays as inputs.