[HN Gopher] Largest-Triangle-Three-Buckets and the Fourier Trans...
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       Largest-Triangle-Three-Buckets and the Fourier Transform (2024)
        
       Author : wonger_
       Score  : 24 points
       Date   : 2025-11-21 16:55 UTC (5 days ago)
        
 (HTM) web link (daniel.mitterdorfer.name)
 (TXT) w3m dump (daniel.mitterdorfer.name)
        
       | kohlerm wrote:
       | It is definitely a real problem to be solved. We used something
       | similar in an IOT application some time ago
        
       | sevensor wrote:
       | > sine waves and provides the amplitude and frequency of each
       | sine wave.
       | 
       | And _phase_! Good luck trying to reconstruct your signal after
       | you discard the phase. Lest you object that nobody would do this:
       | I've seen people actually try to do this, and they couldn't make
       | sense of the garbage that resulted.
        
       | srean wrote:
       | https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93...
       | 
       | is an alternative if visuals are all that matters. It can and
       | will rain havoc in the Fourier space.
        
       | toddwprice wrote:
       | If stuck on a desert island with only one algorithm in my bag,
       | I'd wish for the Fourier. At least I would die happy.
        
       | r--w wrote:
       | Fortunately, if you're a ClickHouse user, you can use the built-
       | in function `largestTriangleThreeBuckets(n)(x, y)`.
        
       | tonyarkles wrote:
       | With respect to the frequency changing as the signal's
       | downsampled, I'm pretty sure the author isn't correctly keeping
       | track of the fact that by having fewer samples they're
       | effectively changing the sample rate. It looks like the FFT every
       | time is using 2048 bins, which is somewhat unexpected. They're
       | not documenting how they're taking a 2048-point FFT with fewer
       | than 2048 samples. Otherwise, fantastic article!
        
       | gblargg wrote:
       | Typically you want the peaks preserved when zooming out.
        
       | jiggawatts wrote:
       | The paper describes the LTTB algorithm on page #21:
       | https://skemman.is/bitstream/1946/15343/3/SS_MSthesis.pdf
        
       | woggy wrote:
       | There is no way the frequency doubled with that first down
       | sampling. Author made a mistake applying the FFT.
        
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       (page generated 2025-11-26 23:02 UTC)