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Weierstrass functions: continuous but not differentiable anywhere

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Re: Weierstrass functions: continuous but not differentiable anywhere

#4

That's pretty much a defining feature of all (infinitely iterated) fractals [1] [1] https://en.wikipedia.org/wiki/Fractal

Cool! I didn't appreciate that. I think its interesting to see that behavior in an everyday Fourier series though.

Re: Weierstrass functions: continuous but not differentiable anywhere

#5
The construction of the Weierstrass function (http://en.wikipedia.org/wiki/Weierstrass_function) was new to me, even though I suffered through a semester of baby Rudin.

To me, the canonical example of a continuous but nowhere differentiable function is: any Brownian motion sample path.

Which, like the Weierstrass function, illustrates that functions that look simple may be so weird that our standard intuition does not apply.

Re: Weierstrass functions: continuous but not differentiable anywhere

#7
post #4

That's pretty much a defining feature of all (infinitely iterated) fractals [1] [1] https://en.wikipedia.org/wiki/Fractal

Cool! I didn't appreciate that. I think its interesting to see that behavior in an everyday Fourier series though.

I'm not sure that I'd call something with an infinite number of non-zero Fourier coefficients an "everyday" Fourier series. :)

Re: Weierstrass functions: continuous but not differentiable anywhere

#9
post #7
post #4

Earlier quoted context omitted.

Cool! I didn't appreciate that. I think its interesting to see that behavior in an everyday Fourier series though.

I'm not sure that I'd call something with an infinite number of non-zero Fourier coefficients an "everyday" Fourier series. :)

Heh. I hear you. But but on the other hand, a sawtooth is perfectly everyday with an infinite series of coeffs: http://en.wikipedia.org/wiki/Triangle_wave .

Re: Weierstrass functions: continuous but not differentiable anywhere

#10
post #3

This function produces an audio signal that sounds like an organ. https://gist.github.com/improv32/8414717 http://vocaroo.com/i/s13ZO9QOMULL

I am quite surprised it does not sound like white noise.

Anyway, I played the output of that script through some filters, and this sounds nice:

play -c 2 weierstrass.wav gain -12 loudness chorus 0.5 0.9 50 0.4 0.25 2 -t 60 0.32 0.4 2.3 -t 40 0.3 0.3 1.3 -s reverb gain 12

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