Natural cubic and linear splines.
function spline (x,y) Defines the natural Spline at points x(i) with values y(i). The natural spline is the spline using cubic polynomials between the points x[i], smooth second derivative, and linear outside the interval x[1] to x[n]. The points x[i] must be sorted. The function returns the second derivatives at these points. With this information, the spline can be evaluated using "splineval". See:
splineval (Splines)
function splineval (x,y,h,t) Evaluates the cubic interpolation with second derivatives h(i) at t The second derivatives can be computed with the function "spline". The spline is a natural spline. I.e., it is linear outside the interval x[1] to x[n].
function linsplineval (x,y,t) Evaluates the linear interpolating spline for (x(i),y(i)) at t The linear interpolating spline is a continous function linear between the points x[i].