I derived a data set with sampling frequency 16384 and want to
interpolate it with a cspline. I want to do so in order to find the true
local maxima and minima of the data, not the discretized visible ones.
However I do not know how to start e.g. root-finding algorithms on the
derivative of the cspline over a small stretch of data as these methods
require explicit C-functions, which I cannot provide. How to proceed?