Cubic spline data interpolation

You also can perform spline interpolation using the

`interp1`

function with the command`interp1(x,y,xq,'spline')`

. While`spline`

performs interpolation on rows of an input matrix,`interp1`

performs interpolation on columns of an input matrix.

A tridiagonal linear system (possibly with several right-hand
sides) is solved for the information needed to describe the coefficients
of the various cubic polynomials that make up the interpolating spline. `spline`

uses
the functions `ppval`

, `mkpp`

,
and `unmkpp`

. These routines form a small suite
of functions for working with piecewise polynomials. For access to
more advanced features, see `interp1`

or
the Curve Fitting
Toolbox™ spline functions.

[1] de Boor, Carl. *A Practical
Guide to Splines*. Springer-Verlag, New York: 1978.