I forgot to send this here to the list _and_ frederico (again, damn)!
Federico wrote:
-----BEGIN PGP SIGNED MESSAGE----- is there an object to compute the derivative function of a signal?
don't know if derivative is the right term.. i mean: f(x)=x => f'(x)=1 f(x)=ln(x) => f'(x)=1/x f(x)=sin(x) => f'(x)=cos(x)
I don't know such as object, but maybe this will help you a little bit: Because you're dealing with finite discrete signals, the derivative of a signal becomes a difference between two consecutive samples. You can easily implement it using [z~] (from zexy, I think) and then subtract the delayed and original sequence:
y[n]= x[n]-x[n-1]
and a more question: has this anything to do with complex signals
I don't think so.
or fourier?
It can, if you wish: derivative corresponds to a multiplication with a ramp in the frequency domain. So, theoretically, you can transform your signal to the frequency domain, multiple with a ramp (watch for 2-sided spectrum), and then, back to time domain, you should have something like "derivative". I have no idea if this works in practice :-) Computation the group delay (=negative derivative of the phase) works using this algorithm, compare http://ccrma.stanford.edu/~jos/filters/Numerical_Computation_Group_Delay.htm...
br, Piotr