Purkinje fiber preparation from a dog heart.

Tags: heart purkinje

Proof of the Pythagorean theorem in Byrne’s The Elements of Euclid.

chrishasaflavor answered: Draw ‘lonely incarnate’ for me.

Pluto on Grindr.

Still think this is one of the best things I’ve ever made.

Reblogged from Icecreamandcake

Using the Fourier Transform to enlarge a real scalar field onto a larger discrete domain should be easy: Transform, add a bunch of zeros to the end, transform back.

Somehow it becomes highly nontrivial in Matlab. I don’t even know what that last one is.

Hey! I know this one! Matlab FFT is two-sided starting at 0. Your data vector corresponds to frequencies 0,1/K*2pi,2/K*2pi…pi…K-2/K*2*pi,K-1/K*pi. So your (end) element is  X(-1/K). In order to pad zeros to the FFT you have to instert them in the middle.

Yes, this much I know. The wave numbers run, not from zero to N/2 for real signals, but from -N/2 through 0 to N/2 -1. This is somewhat nonstandard [^1] but not too confusing. Trefethen deals with it in his typical ease, why can’t I?

However, did you know that if you take a ‘symmetric’ signal, say $$u : u - \mathtt{rot90}(u, 2) = 0$$, and try to enlarge it [^2], the result will not satisfy that condition? The second graph is the result of such a failure.

[^1]: and boy do I hate it

[^2]: suppressing the Nyqvist mode of course

Reblogged from Un Café Triple
Tags: matlab fft

Everything is terrifying me today.

Reblogged from joaniepepperoni

"Say, lad, did you know that I can make myself uglier yet?"

The Sword in the Stone (1963)

Reblogged from D [E] B R I S

You have been judged by Portia de Rossi. Have a nice day.

Using the Fourier Transform to enlarge a real scalar field onto a larger discrete domain should be easy: Transform, add a bunch of zeros to the end, transform back.

Somehow it becomes highly nontrivial in Matlab. I don’t even know what that last one is.

Tags: matlab

Amplitude snapshot $$|u|$$ for the Complex Ginzburg-Landau field equations.

I like singular fields.

Tags: matlab cgle