On 07/11/2010 01:13 PM, David Goldsmith wrote: > Hi! I'm a little confused: in the docstring for numpy.fft we find the > following: > > "For an even number of input points, A[n/2] represents both positive and > negative Nyquist frequency..." > > but according to http://en.wikipedia.org/wiki/Nyquist_frequency (I know, > I know, I've bad mouthed Wikipedia in the past, but that's in a > different context): > > "The *Nyquist frequency*...is half the sampling frequency > <http://en.wikipedia.org/wiki/Sampling_frequency> of a discrete signal > <http://en.wikipedia.org/wiki/Discrete_signal> processing system...The > Nyquist frequency should not be confused with the /Nyquist rate > <http://en.wikipedia.org/wiki/Nyquist_rate>/, which is the lower bound > of the sampling frequency that satisfies the Nyquist sampling criterion > for a given signal or family of signals.../Nyquist rate/, as commonly > used with respect to sampling, is a property of a continuous-time signal > <http://en.wikipedia.org/wiki/Continuous-time_signal>, not of a system, > whereas /Nyquist frequency/ is a property of a discrete-time system, not > of a signal." > > Yet earlier in numpy.fft's docstring we find: > > "...the discretized input to the transform is customarily referred to as > a /signal.../" > > Should we be using "Nyquist rate" instead of "Nyquist frequency," and if > not, why not?
No, because we are dealing with a discrete time series, and our usage corresponds exactly with the Wikipedia description that you quote. Eric > > DG > > > > _______________________________________________ > NumPy-Discussion mailing list > [email protected] > http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
