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Largest-Triangle-Three-Buckets and the Fourier Transform (2024) (daniel.mitterdorfer.name)
sevensor 73 days ago [-]
> 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.

tonyarkles 73 days ago [-]
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!
srean 73 days ago [-]
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.

r--w 73 days ago [-]
Fortunately, if you’re a ClickHouse user, you can use the built-in function `largestTriangleThreeBuckets(n)(x, y)`.
jiggawatts 73 days ago [-]
The paper describes the LTTB algorithm on page #21: https://skemman.is/bitstream/1946/15343/3/SS_MSthesis.pdf
toddwprice 73 days ago [-]
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.
woggy 73 days ago [-]
There is no way the frequency doubled with that first down sampling. Author made a mistake applying the FFT.
kohlerm 73 days ago [-]
It is definitely a real problem to be solved. We used something similar in an IOT application some time ago
gblargg 73 days ago [-]
Typically you want the peaks preserved when zooming out.
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