Cubic spline data interpolation.

  Given data vectors X and Y, and a new abscissa vector XI, the

  function YI = SPLINE(X,Y,XI) uses cubic spline interpolation

  to find a vector YI corresponding to XI.



  Here's an example that generates a coarse sine curve, then

  interpolates over a finer abscissa:



      x = 0:10;  y = sin(x);

      xi = 0:.25:10;

      yi = spline(x,y,xi);




  PP = spline(x,y) returns the pp-form of the cubic spline interpolant

  instead, for later use with  ppval, etc.



  See also INTERP11R8IXB5, INTERP21R8IYB5, PPVAL6G179S, MKPP3AEUNE7, UNMKPPGQE3BU, the Spline Toolbox.