[PD] Spectrum graphing amplitude problem

Jason Plumb jason at noisybox.net
Mon Oct 22 03:20:02 CEST 2007

Mathieu Bouchard wrote:
> The most rapid change you can have in a signal is an alternance of two 
> values: e.g. +1, -1, +1, -1, +1, -1, ... which has S/2 frequency.

Woah, that's a *super* good way to remember that.  Thanks.  I love 
examples, and that's great!

Charles Henry wrote:
 >> Any other ideas?
 > Another option is to use the 'plot as points' graph.  You will get all
 > the points that way, even if the size is too small.

I would do that, but the single points are just too hard to see IMO.

 > If you're using fft~, you will see the full spectrum from 0 to N-1,
 > where the second half of the spectrum is the conjugate of the first
 > half.  For graphing purposes, you will probably just need the first
 > half.

That's cool, makes sense.  Since I now understand that I'm dealing with 
a graph/display issue, maybe I need to do some heavier lifting?  That 
is, unless somebody can suggest a better way, I guess I'll try and do 
block-synchronized snapshots, somehow walk/traverse the fft results 
myself and look for local discretized maximums.  Doesn't seem like much 

The real truth is that although I stand to learn a thing or two by going 
down this road, I'm probably just reinventing the wheel and could drop 
in an existing spectrum abstraction or external huh?


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