4.6. What is the Spectrum object ?ΒΆ
Normally Users should not be bother by the classes used. For instance if you use the pburg class to compute a PSD estimate base on the Burg method, you just nee to use pburg. Indeed, the normal usage to estimate a PSD is to use the PSD estimate starting with the letter p such as parma, pminvar, pburg, (exception: use Periodogram instead of pPeriodogram).
Yet, it may be useful for some advanced users and developers to know that all PSD estimates are based upon the Spectrum class (used by specialised classes such as FourierSpectrum and ParametricSpectrum).
The following example shows how to use Spectrum. First, let us create a Spectrum instance (first argument is the time series/data):
from spectrum import *
p = Spectrum(data_cosine(), sampling=1024)
Some information are stored and can be retrieved later on:
p.N
p.sampling
However, for now it contains no information about the PSD estimation method. For instance, if you type:
p.psd
it should return a warning message telling you that the PSD has not yet been computed. You can compute it either independantly, and set the psd attribute manually:
psd = speriodogram(p.data)
or you can associate a function to the method attribute:
p.method = minvar
and then call the function with the proper optional arguments:
p(15, NFFT=4096)
In both cases, the PSD is now saved in the psd attribute.
Of course, if you already know the method you want to use, then it is much simpler to call the appropriate class directly as shown in previous sections and examples:
p = pminvar(data_cosine(), 15)
p()
p.plot()
