Hi, Le 21/10/2013 15:58, Todd a écrit : > On Mon, Oct 21, 2013 at 3:13 PM, Pierre Haessig > <pierre.haes...@crans.org <mailto:pierre.haes...@crans.org>> wrote: > > 1) is the terminology "phase" vs. "angle" spectrum standardized ? > I must > say I've never heard of one meaning "wrapped" and the other > "unwrapped". > I didn't find similar terms in Matlab docs, but I didn't search that > thoroughly. > > > The "angle" function in numpy returns the wrapped angle, while the > "unwrap" function documentation talks about phase, so it is consistent > with the usage in numpy. Further, in signal processing, phases can > have any value, while "angle" often refers to the angle between two > lines, which must be wrapped. > > There may be some ambiguity, but I made sure to explain it in the > documentation and provide links between the two functions so people > know what they should do if they want to use the other approach. > > > 2) Should there be two separate functions for these two, or just one > function, with a switch argument `unwrap` ? (I guess it would be > True by > default) > > > I originally was going to do that, but decided against it. The > problem is with specgram. Here, I thought it would be needlessly > complicated to add an "unwrap" parameter that is only useful for one > "mode". To make it obvious to users, I wanted to keep specgram as > similar as possible to the other plot types, and that involved keeping > the parameter. > > Further, this approach is simpler to code and easier to maintain. > Having to deal with the "unwrap" parameter would have been more > difficult to program. Dealing with both an "unwrap" parameter in some > cases and a separate "mode" in others would have been even more > complicated. > > Further, _spectral_helper and specgram already have a huge number of > arguments. This way I was able to get away with just adding one new > argument rather than two. > Thanks for the feedback. I agree that your documentation does make clear the distinction between "phase" and "angle" and that it has a consistency. I just feel that this distinction does not exist "outside" ...
But beyond this question of phase vs. angle, I must say I don't see that big a use case for phase/angle spectrums[*] (as opposed to magnitude which are much used). Also, in many cases, "spectrum" is synonymous with spectral density, which implies "magnitude". In the end I wonder whether the notion of phase even makes sense for a spectrogram ? That's the reason why I'm a bit skeptical with the many new "mode switches" in the spec helper, along with the new phase/angle_* functions. best, Pierre [*] On the other hand I do see a usecase of magnitude and phase for plotting transfer functions (i.e. Bode diagrams). Those are not fft based plots, so it's a different topic I guess. Bode/Nyquist/Black diagrams could be nice to have.
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