There are may "Cubic Splines". Some doing best/worst
depending the application. Reading this document, you
will know how its works inside Mathcad 11 and earlier
and Matlab about their l, p, c ... as well you will be
able to differentiate with Smath 'ainterp, cinterp'.

It may become important in case Smath Designers intend
to compose an ODE wrapper Mathcad style that would
output a scalar result for the canvas plot. With those
subtile distinctions, results may vary.

Jean

Spline l_p_c.sm (154 KiB) downloaded 64 time(s).