Envelope of a signal.
Computes the envelope of the given data which can be windowed or not. The envelope is determined by the absolute value of the analytic signal of the given data.
If data are windowed the analytic signal and the envelope of each window is returned.
Parameters: data (ndarray) Data to make envelope of. Returns: A_cpx, A_abs - Analytic signal of input data, Envelope of input data.