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spacedomeon MIT moves all classes online for the rest of the semester

In Massachusetts they are state police (at UMass at least)

spacedomeon Netlify raises $53M Series C as microservices approach to web development grows

This has been my issue as well, I started using their analytics when it launched. I thought they must still be working on it from the state its in, it is absolutely not worth the cost currently. You cannot even see the data from the previous months! Despite having paid $9 for them just to store page view totals.

spacedomeon Siggraph2019 Geometric Algebra (2019) [video]

In the video they present it as an algebraic framework where you can "add" to a number system elements x such that x^2 = -1, x^2 = 0, or x^2 = 1. Adding the element x^2 = -1 to the real numbers gives you the complex numbers, with x = i. Adding the element x^2 = 0 to the real numbers gives you the dual numbers with x = epsilon, which is what can be used for automatic differentiation. The case of x^2 = 1 is more complicated.

spacedomeon Let's remove quaternions from every 3D engine (2018)

Amusingly the discovery of Quaternions by Hamilton was also followed by arguments within the mathematical community as to whether mathematics should be rewritten in the language of quaternions, as Hamilton proposed to do and subsequently spent the rest of his life pursuing. Initially many mathematicians found them confusing, Hamilton's book is unusually difficult to read and there were no others. The work of Grassmann was somewhat neglected at the time, and eventually the Gibbs/Heaviside notion of vectors (essentially what we use today) emerged as a competitor to the quaternions. It seems it was a particularly bitter mathematical divide, up there with Newton vs Leibniz. Here is a quote by Tait, one of the "quaternionists":

"Even Prof. Willard Gibbs must be ranked as one of the retarders of quaternion progress, in virtue of his pamphlet on Vector Analysis, a sort of hermaphrodite monster, compounded of the notations of Hamilton and of Grassman"

See "History of Vector Analysis" by Crowe or "Hamilton, Rodrigues, and the Quaternion Scandal" by Altmann. Nice to see the author cites these!

The Geometric Algebra comes from Clifford Algebras, which where an attempt to combine Hamilton's Quaternions and Grassmann's forms, and in fact contains both as sub-algebras. In the case of 3D rotations calling them Rotors or Quaternions seems mostly like a different way of thinking about the same thing.

I think this would be more kindly put as "reimagining" quaternions and not "removing" them. The additional geometric intuition from GA does seem useful, and even as someone who has used quaternions extensively (though in a very different context), I would also choose to work with Geometric Algebra as a framework for geometry over Quaternions.

The visualizations are quite good here, it is a good way to understand bi-vectors, you can wiggle them about a bit in 3D instead of just staring at parallelograms on a page. The only criticism I have is that they say quaternions and the cross product come "out of nowhere", but then the way they present the geometric product is equally "out of nowhere".

spacedomeon Into the Personal-Website-Verse (2019)

https://spacedome.tv

Made with hugo and hosted on netlify, static with no javascript. It's a bit empty but I'm still working on it.

spacedomeon Science Books of 2019

Perhaps a slightly different sort of science book, but I highly recommend "Foundations of Applied Mathematics" by by Humpherys, Jarvis, & Evans, the first volume of which was published in 2017, and of which the second supposedly will be published in 2019. Volume 1 is good overview of the Analysis needed in various applications, they give as examples "analysis, optimization, probability, statistics, differential equations, machine learning, and control theory". I found it useful as an overview of the theory one might need in a unified exposition, with a modern and pragmatic choice of topics and notation. Learning the topics previously from many books, all with different notations and ideas of pedagogy, can be confusing (to me at least), especially in understanding how different parts of the theory are interrelated. It even comes with computational "labs", the code for which is available freely online, something often lacking in books on numerical analysis, applied math, etc. My only complaint is that it somewhat leaves out differential equations. Definitely worth looking at! In particular the chapter on matrix calculus.

spacedomeon How to Show Available WiFi Networks on Linux from the Command Line

If you switch to iwd from wpa_supplicant there is also iwctl.

spacedomeon Statistics with Julia [pdf]

I've found Plots.jl and PyPlots.jl to work well for most basic things, despite not always being entirely pleasant to use, for example the compilation time issue, but this should hopefully improve. The only real problem I had is that these are not quite sufficient for plots to be published in a paper, many visual tweaks you might want are broken or terribly documented, and I have to just use matplotlib or R. It is generally great for jupyter notebooks though. I see the current deficiencies as highlighting just how much work went into matplotlib and others to get where they are today (and even mpl is in some ways still lacking, for example 3D surfaces and meshes). It is unfortunate though, as plotting is a core functionality for their main target of computational science. But to answer your question, mostly yes. Everything seems to be slowly improving though.

spacedomeon Ask HN: Resources to learn real analysis?

An interesting supplementary book is "Analysis by Its History" that gives insight into how classical analysis was actually developed. Not so great to learn from initially, but gives some background on the intuitions from which the modern definitions are based.