HNHacker News
TopNewBestAskShowJobs

johndcook

5,946 karma · joined July 27, 2009

https://www.johndcook.com/blog/expert-hipaa-deidentification/
submissionscomments
johndcook··on Why Mathematica does not simplify sinh(arccosh(x))
Thanks. That was a mess. Don't know what happened, but I fixed it this morning.
johndcook··on Text case changes the size of QR codes
Fixed again. I missed one. :)

Thanks.

johndcook··on Text case changes the size of QR codes
Thanks. Fixed.
johndcook··on Mollweide map projection and Newton's method
Yes. Thanks.
johndcook··on A recipe for creating random fractals
The original post had an error. I just updated the post with a correction.
johndcook··on Evaluating a class of infinite sums in closed form
I believe the SVG file has a transparent background, but the img tag has style="background-color:white". Some browsers honor the background-color setting and show a white background behind the equations, even in dark mode. Some do not, and so the equations appear as black-on-black.

It would be better if I altered the SVG image itself to set the background color, but I don't know how to do that. Suggestions are welcome.

johndcook··on Evaluating a class of infinite sums in closed form
Thanks. Fixed.
johndcook··on Evaluating a class of infinite sums in closed form
Thanks. Fixed.
johndcook··on A formula for the nth digit of 𝜋 and 𝜋^n
The paper begins by citing an equation that isn't explicitly in the book referenced. I wrote up some notes filling in a few missing details.

https://www.johndcook.com/blog/2023/01/16/pi-bernoulli-numbe...

johndcook··on Dogs poop in alignment with Earth’s magnetic field, study finds (2014)
The comments here are in line with what I vaguely remembered:

https://news.ycombinator.com/item?id=22276468

johndcook··on Dogs poop in alignment with Earth’s magnetic field, study finds (2014)
I don’t have a reference, but I believe I read an article explaining that this theory was based on selective data and that in fact dogs have no direction preference.
johndcook··on SARS-CoV-2 contains part of a patented genetic sequence
Are you suggesting the editors of Frontiers in Virology are not serious virologists?
johndcook··on A “proliferation of administrators”: faculty reflect on rapid expansion
Burying the lede: Yale now has more administrators than undergrads.
johndcook··on An Annoying Problem
The title doesn’t give a hint of what the problem is or why it’s annoying, but it’s an interesting problem: how efficiently can you determine whether two finite groups are isomorphic. It’s annoying because it seems it should be easier than it is, given that you have so much structure to work with.
johndcook··on Floor, Ceiling, Bracket
Agreed. Say he introduced 100 bits of notation, 3 good and 97 bad. The net result is that the world absorbed 3 good ideas, and the rest have vanished from memory. Not a bad track record. I hope to give the world three good ideas.

Besides notation, APL introduced some ideas about vector computing that have been adopted in languages like R and Python (NumPy).

johndcook··on Effectiveness of Mask Recommendation to Prevent SARS-CoV-2 (Randomized trial)
p = 0.38?!

Nobody would take a p-value of 0.38 as evidence. There are a lot of problems with p-values in general, but even uncritical fans of p-values would ignore any study with p = 0.38.

johndcook··on Floating point oddity
Right. Sorry for the confusion. The post hit HN while I was editing.
johndcook··on Floating point oddity
I thought there was a difference between a C and C++ implementation, but it was an error on my part. When I fixed the bug, I changed the post title. But the post hit HN while I was in the process of fixing it.
johndcook··on How category theory is applied
Here's an example. It's not mentioned in the OP, but in a link in the OP. Microsoft's LINQ was designed using principles from category theory. They didn't use category terminology in the final product, and rightfully so.
johndcook··on Rare and strange ICD-10 codes
Not everything that has happened once can have its own code. There must be things that happen more frequently that don't have their own code.
johndcook··on Rare and strange ICD-10 codes
Traditional Chinese Medicine? That would be interesting.
johndcook··on Ask HN: How Would You or Did Convince Your Boss That You Can Work Remote?
I said "We're out of office space. If you want to keep hiring, we have to let people work from home." He accepted that immediately, and we moved on to logistics.
johndcook··on Projecting Unicode to ASCII
Thank you for maintaining this package. I wish I'd run across it sooner.
johndcook··on Ellipsoid distance on Earth
Yes, the author does write a lot of scientific code and is in the habit of using SciPy. -- the author :)
johndcook··on Riemann hypothesis, the fine structure constant, and the Todd function
Rumor has it that his most recent proof also received private criticism and he rejected it. But the experts are being discreet. They're not jumping on twitter. Instead you had unqualified people who hadn't seen the papers or the talk saying that it had to be wrong.
johndcook··on The quadratic formula and low-precision arithmetic
Posits are a hardware-friendly implementation of unums, a sort of halfway house on the road to Gusafson's full vision of unums. Posits have a fixed size and are meant to be a drop-in replacement for IEEE floats. They can and are being implemented in hardware.

Unums are more ambitious. They would have variable lengths, so implementing them would require more changes than just changing the way a fixed-length set of bits is interpreted.

johndcook··on Planets evenly spaced on log scale
True, but the article doesn't mention a more accurate theory. It implies that the rule works better than we have theoretical reasons to expect. (But as I commented above, the article contradicts itself to some degree.)
johndcook··on Planets evenly spaced on log scale
The Wikipedia article is contradictory. As you quoted, it says that the law works well in simulation and in observation, and yet it's just a coincidence. Of course it's not exact, but it looks like a very good first approximation.
johndcook··on Approximating a solution that doesn't exist (2009)
re book recommendation: Lawrence Evans's book Partial Differential Equations. Functional analysis etc.
johndcook··on Distance to Mars
The results in the blog post wouldn't do to launch a probe, but they do give you a good idea of how the distance varies over time. It's a little surprising that such a simple calculation works as well as it does. More accurate calculations would be interesting, much more complicated.
Page 1 of 4Next →