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keithalewis

Re:Excel now supports multiple values in a single cell on Saturday September 26, 2026 @07:47AM (#49855629)
How about adding the time dimension to Excel? https://www.xllmonte.com/
Re:A wild 'freakosystem' has been born in Hawaii on Thursday April 10, 2025 @06:21PM (#43648580)
I see what you did there.
Re:Introduction to Stochastic Calculus on Monday February 24, 2025 @02:32PM (#43163853)
There is no need for it. Here is a simple replacement: https://keithalewis.github.io/math/um1.html.
Re:Beej's Guide to Git on Monday February 10, 2025 @07:21AM (#42999445)
Linus wrote it, so there's got to be a pony in there somewhere. He's the first person in the world to figure out version control software. /s
Re:Beej's Guide to Git on Monday February 10, 2025 @12:15AM (#42997166)
Thank you for your diligence in explaining complicated topics in a way that makes them accessible to people trying to learn what people before them figured out. You are a true educator that seems have found a place to support you to continue doing that.

Are you concerned that your git exposition is much longer than the other guides you have produced?

Re:The Tensor Cookbook on Sunday February 02, 2025 @12:15AM (#42906089)
The Wikipedia page on this is sufficient. If F:X -> Y is a function between normed linear spaces then DF:X -> L(X,Y), where L(X,Y) is the vector space of linear operators from X to Y, satisfies F(x + h) = F(x) + DF(x)h + o(h). A function is differentiable if it can be locally approximated by a linear operator.

Some confusion arises from the difference between f:R -> R and f':R -> R. It's Fréchet derivative is Df:R -> L(R,R) where Df(x)h = f'(x)h. Row vectors and column vectors a just a clumsy way of thinking about this.

BTW, all you need in order to publish on arixv.org is to know a FoF. There is no rigorous peer review. https://arxiv.org/abs/1912.01091, https://arxiv.org/abs/2009.10852.

Re:The Tensor Cookbook on Friday January 31, 2025 @10:29PM (#42895379)
"This book aims to standardize the notation for tensor diagrams..." https://youtu.be/zELbzXAmcUA?t=73
Re:The Tensor Cookbook on Friday January 31, 2025 @10:15PM (#42895305)
The author also seems to be unaware of Fréchet derivatives.
Re:The Tensor Cookbook on Friday January 31, 2025 @04:38PM (#42892431)
This is incomplete, incorrect, and irrelevant. Standard notation already exists. I'm sure it is fun to draw squiggly lines and some people enjoy reinventing the wheel. Spend some time learning what others have taught us before striking out on your own lonely path.
Re:Kalman Filter Tutorial on Sunday January 19, 2025 @01:27PM (#42759903)
Your statement "the best path forward for me understanding is a path that can maintain that curiosity" comes off as entitled. Only you owe yourself that.

"I can play with Arnold's cat and, slowly, through no scientific rigor..." You are fooling yourself into believing you understand if you leave out rigor. If your post has the words "I" and "me" in every other sentence, maybe you should consider whether or not you are adding value for others in the online discussion.

I doesn't cost you anything to ask other people to do things for you, and you will no doubt find other thoughtless people chiming in about your right to do that. If everything you need is not at your fingertips already, maybe no amount of handholding will help.

Re:Kalman Filter Tutorial on Saturday January 18, 2025 @08:05PM (#42752763)
There is no royal road. You only need to put in a fraction of the effort people before you did. You may be just too dumb to ever understand what brilliant people before you devoted their life to. And that's okay. Just stop whining about it in public.
Let S = {1, 2}. Every distance function is determined by d(1,2) = a, a >= 0. Define f(d) = {{1,2}} if a = 0 and f(d) = {{1},{2}} otherwise. Isn't this a clustering algorithm that is scale invariant, rich, and consistent?
Re:Quiver: A Modern Commutative Diagram Editor on Friday December 27, 2024 @04:09AM (#42520891)
It only takes one woke gatekeeper with karma to downvote on HN.
Re:Quiver: A Modern Commutative Diagram Editor on Friday December 27, 2024 @03:10AM (#42520647)
You made a completely obvious and true statement starting with "It would help..." That seems to be frowned upon on HN.

BTW, a simpler definition of a (small) category is that it is a partial monoid.

We agree. The case was about Renaissance breaking the law. The best lawyers their money could buy lost and did not avail themselves of their right to appeal. The ruling body found they were tax cheats.

Philanthropic work is great way to get shills to come out of the woodworks.

Re:Category Theory in Programming on Friday December 13, 2024 @08:09PM (#42413779)
Category theory is just another way of looking at math besides the impoverished notion "everything is a set". Mathematics is used in computer science. Rust is a great example. Jean-Yves Girard invented linear logic to make Gerhard Gentzen's sequent calculus symmetric, similar to Paul Dirac's theory that led to the discovery of positrons. Girard's concern about using a proposition exactly once in a proof led to borrow checking.

Putting on category theory glasses can help discover and clarify new facts. Thinking in terms of objects and arrows leads to duality: reverse the direction of the arrows.

The category Set is only one of many categories. The objects are sets and the arrows are functions. A function I -> S that is 1-1/injective/mono[1] corresponds to the set theory notion of a "subset". The dual is a function S -> I that is onto/surjective/epi[2]. What set theory notion does this correspond to?

Hint: Look into David Ellerman. He is the von Neumann of our times.

[1] f is mono if fg = fh implies g = h. [2] f is epi if gf = hf implies g = h.

Hi Dang.

Re:Parkinson's Law: It’s real, so use it on Thursday December 12, 2024 @09:08AM (#42399219)
This. Motivation is the key to getting employees to produce over a period of time. Give the good ones the maximum amount of ownership they can handle and they will set an example for everyone else. Grow the talent over time.

Fire the whinny shit-talkers as soon as possible. They drag everyone down.

Re:Timemap.org – Interactive Map of History on Thursday December 12, 2024 @08:03AM (#42398795)
And, like, a LARPing mode I could use while sitting in my mom's basement that would automagically post every brain fart I had to HN. That would be totally cool!
Re:The Rules of Programming on Monday December 09, 2024 @05:04AM (#42364631)
When I worked at Bloomberg their first coding guideline was "Don't sweat the small stuff." I was mystified by that when I first read it. Then I sat in meetings where someone would drone on about how clever they thought their code was until someone asked "Is this small stuff?" It would shut them up so we could move on to more important matters.
Re:Square Roots and Maxima on Saturday November 30, 2024 @01:57PM (#42283300)
Front page material? P(max{X_1, X_2} <= x) = P(X_1 <= x, X_2 <= x) = P(X_1 <= x) P(X_2 <= x) = xx. P(sqrt(X_3) <= x) = P(X_3 <= x^2) = x^2. It is late in the day when midgets cast long shadows.
Re:Time-series forecasting through recurrent topology on Sunday November 24, 2024 @07:19AM (#42227559)
You are missing what is missing. Their source code does not fill in the missing pieces.
Re:The Deceptively Asymmetric Unit Sphere on Friday November 22, 2024 @10:00PM (#42218885)
Never underestimate the power of das blinkenlights to entertain lazy dumb people.
Re:Mathematical Thinking Isn't What You Think It Is on Friday November 22, 2024 @03:42AM (#42212157)
I work hard to be lazy.
Re:A binary tree of all Pythagorean triples on Friday November 22, 2024 @03:32AM (#42212116)
There are Pythagorean triples (a, b, c) for which there do not exist integers m, n with a = m^2 - n^2, b = 2mn, c = m^2 + n^2.
Re:Differential Dataflow for the Masses on Friday November 15, 2024 @10:57AM (#42148047)
Just pointing out what the theoretical documentation says. A stream should have operations for empty, current, and next. You don't want implementation details leaking into the abstract model.
Re:Differential Dataflow for the Masses on Wednesday November 13, 2024 @04:15PM (#42130071)
This seems to make the mistake of identifying a vector with a stream.
Re: on Thursday November 07, 2024 @08:28PM (#42083191)
HN spamtroturfing one of their own startups? I'm shocked, shocked!
Re:Axiomatics: Mathematical thought and high modernism on Sunday November 03, 2024 @04:57PM (#42036394)
What is a delta function at a composed with a delta function at b <> a?

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