andy_wrote

I've recently started going through Axler carefully and doing the problems, a quarantine activity I guess, and have been enjoying it. I actually learned about this book on an older HN post.

It does have plenty of matrices. The main thing it really does is avoid determinants until the very end. The determinant is certainly something I remember learning as a kind of rote operation, without really understanding any intuition behind why you'd multiply and add these numbers in this particular way. I still feel lacking in "feel" here, which is why I suppose I'm going through Axler now.

The asset value underlying an ETF can be negative, but then the owner of the ETF will just have a worthless piece of paper. The ETF managers will have a problem on their hands regarding the negative amount, though.

In contrast, a futures contract is an agreement to make a future trade, so it can keep going against you past 0. If you are able to take physical delivery, your worst-case scenario is that you pay the money you said you would, and you get your oil. But if you are a casual day-trader type, you probably don't have the ability to take physical, so you may be in trouble (over a barrel, literally).

I agree with you about the dangers of ETFs and about knowledgeability. I didn't mean to advocate for ETFs on an absolute basis, just to make a relative statement about them vs. futures.

I'm not recommending USO or oil itself as an investment, and I agree that you will be paying money to the ETF manager if you get involved in it.

But I don't agree that USO is _more_ dangerous for a casual trader to trade than oil futures, for the reasons I mentioned.

Removing the overall fluctuations of the oil market, the relative problem with ETFs is that they bleed away value over time. That's a real issue, but I wouldn't compare that to juggling a live hand grenade.

Edit: you did not say it was more dangerous, my mistake. I do think that ETFs are less dangerous, for the reasons I mentioned.

There are ETFs that track oil futures (basically like a stock, but backed by oil instead of a company). It's been a while since I've looked at any of this, but I think USO is still the most prominent.

There are plenty of things to watch out for with these ETFs. You pay ongoing expense fees. And ETFs, especially those that aren't just holding containers for assets, can have subtleties in their prospectuses that cause their value to fluctuate in counterintuitive ways. There's still a lot to be cautious about.

However, compared to the actual futures, they're more suitable for casual investors, for reasons such as what we see here. They can't go below 0 and don't necessarily involve margin. And the ETF will typically deal with things like rolling the futures position ahead of expiry.

I don't know that this is regional so much as colloquial vs. formal. In the US people recognize that the subjunctive is technically correct and use it in formal writing. But it's very common to violate this rule in speech, so much so that to my ears it sounds less "wrong" than "informal."

As far as musicians go, you can find examples of people on both sides of the pond using or not using the subjunctive. Beyoncé sings "If I were a boy," while Thom Yorke sings "I wish I was special."

Based on my experience learning Czech (not native at all, just interested):

- it's typically listed as a separate letter when writing out the alphabet

- but in practice it's typed out as "c h" and not as a single character

- it occupies its own place in Czech standard alphabetical order, my English-Czech dictionary has all the "ch" words after "h" (so interestingly in order to do a proper sort programmatically you need to possibly look 2 characters ahead)

Since last Friday I've been making my Zoom virtual background a daily rotation of artwork. It's been a fun and educational experience for me (I'm no art expert, just a casual fan of museums) and I think my friends and co-workers have enjoyed it. When you're mostly stuck at home all day it's nice to have a daily "new" to look forward to.

I've been recording my choices and when this is over I'll have a little "Zoom Museum" as a kind of artistic memorial of the pandemic.

This link is a great source for new art, so thank you OP!

I think the part that you have correctly included that people forget or elide is that it's the probability under a specific null hypothesis. So it's a function of what you have chosen for that - normal distributions, a certain parameter value of 0, etc. So this means that a) it's not the probability you'd see in the real world under repeated performance b) it's not the probability under other reasonable null hypotheses. Like maybe under the hypothesis parameter = 0 you get an improbably large p-value, but under parameter = 0.1, or with different assumed underlying distributions, you wouldn't see something so extreme.

I'd guess that the original writer understands this, and that Gelman is only pointing it out because casual readers sometimes don't mentally retain the full baggage that the p-value carries.

Maybe For Better or For Worse? Most prominent example of a daily comic strip I can remember where characters age in real time.

Watterson highlighted that arc in his 10th anniversary collection (which is a really wonderful collection of essays and explanations side by side with strips). It happened relatively early into the comic strip's life and IIRC he regarded it as a turning point in Calvin & Hobbes's ability to move beyond gags and handle weightier topics.

There are a lot of crossword constructors who publish/sell their puzzles independently on the Internet, and often they create both puz and pdf files. Some sources of free ones:

- Brendan Emmett Quigley: https://www.brendanemmettquigley.com/

- Paolo Pasco: http://gridsthesedays.blogspot.com/

- and see the sidebar of Paolo's blog for links to many more constructors

- They stopped publishing these online, but the Chronicle of Higher Education has several old crosswords here: https://www.chronicle.com/section/Crosswords/43

It would be interesting to see how realistic a cat thinks these are, maybe by measuring brain activity or reactions. It's possible that a cat may not be fooled by cats we think look real, or perhaps more interestingly, that a cat is fooled by a not particularly good image.

Common cuckoos lay their eggs in other birds' nests. The chicks don't necessarily look much like the host species to the human eye, but they can fool their hosts along the correct dimensions to get food from them. It's an interesting question to what degree ML algorithms trained on human dimensions could be foiled by an animal whose brain has been wired for different perceptions, or how feasible it is to train an ML algorithm on animal perception, or if it's possible to make an algorithm that successfully fools, say, both man and dog.

On the last point, for example: to make fake sounds that fool animals with different hearing ranges, presumably you have to be able to output sounds across the union of the ranges and train on sound data over the union of the ranges.

(Note: I'm not a biologist, if someone more informed wants to correct me on anything here you are welcome to do so.)

> Spend 50% of the writing time actually writing, the rest tweaking, reading and illustrating. Details are important.

I find this true not just of blog posts, but any time I've done formal writing at all. There is an immense gulf in quality between writing that has gone through even just one heavy edit/revision process and writing that never has.

I've recently been encouraging my technical co-workers to expend more time on not-code, such as documentation, tutorials, plans, postmortems, internal RFCs, carefully worded PR/commit comments, etc. One challenge is that people sometimes think that when they "finish" a piece of writing, they're done. Unless you've been iteratively revising pieces of it in smaller chunks, I think you're really only halfway there.

I haven't made the donation yet for 2018, but I make donations every year right at year's end to at least these two charities:

- Doctors Without Borders

- Direct Relief

Global health problems is where I'm most interested in donating money. I split my money between those two primarily to have a little diversification from idiosyncratic risks to a single operation.

These occupy the vast majority of my charitable giving. I give or have given in the past much smaller amounts to a smattering of other charities: Wikimedia, Give Directly, ACLU, Planned Parenthood, Lambda Legal, Girls Who Code.

Also: I'm an avid crossword solver, and over the last year or two some puzzle constructors, as a way of doing good, have started offering packets of crosswords in exchange for donations to a cause. The original, I believe, was Francis Heaney's Puzzles for Progress http://puzzlesforprogress.francisheaney.com/ for broadly progressive causes, but I have also seen Queer Qrosswords https://queerqrosswords.com/ for LGBTQ charities and Women of Letters https://www.pattivarol.com/women-of-letters/ for feminist charities. If it tips you over the edge to donate, do it and go get some puzzles!

Some good ones I read this year:

- _SPQR_, by Mary Beard. Engaging book surveying the history of ancient Rome, mostly Republic and early Empire if I recall correctly.

- _To Explain The World_, by Steven Weinberg. History of physics from the ancients to about the time of Newton. Don't skip the technical notes! Actually do the problems!

- I reread _Wolf Hall_, by Hilary Mantel, it was as good as I remember. This time through, I also spent some time on the Internet tracing the histories of the major characters before and after the events of the book, and it really enhanced my appreciation of it. (I also read, for the first time, its sequel, which was fine but not quite as good.)

Yes! Although I was an econ major I did the same thing, I dipped my toes into pure math and took some real analysis and abstract algebra. I really found these challenging at times. But the ideas and modes of thinking I gained from these classes have been very rewarding since.

I relate its value in programming to the Torvalds adage "Bad programmers worry about the code. Good programmers worry about data structures and their relationships." Taking some abstract algebra really helps you think about data structures and their relationships, and to architect "good bones" in your code.

Yeah, I'd be very interested to learn about anything about the sensitivities of ridership to other external variables in general.

Looking at the article's linked presentation [1] and the MTA's most recent financial plan [2] it seems like all the hurt is coming from really huge declines in projected revenues - labor costs seem to be growing pretty reasonably but there's basically zero projected growth in fares. If someone can give me a layman's explanation of what "Capital and Other Reimbursements" is, which accounts for about a $500mm decline between 2019 and 20222, I'd be much obliged.

So I am curious how sensitive riders are to the increased service problems, how much that makes them switch out, to get some sense as to how much the signal improvements will help solve this problem. Also how much to a fare hike, which seems like the more straightforward answer in a vacuum (i.e. other than taxes or other government infusions). The MTA says in [1] that even "draconian service reductions would have a relatively small impact on the deficit."

[1] - http://web.mta.info/news/pdf/MTA-2019-Final-Proposed-Budget-... [2] - http://web.mta.info/news/pdf/MTA-2019-Final-Proposed-Budget-...

I don't know anything about the Israel-Intel deal and have not decided personally how I feel about HQ2 in NYC. But I upvoted your comment because it emphasizes looking at other historical deals, and not just the projections and analysis on the current deal, and would love to read more of that in this discussion. This is a very large project over long horizons (10yrs) and it's hard to imagine being anything but extremely uncertain about projections; you have to look at history.

I'm also a sports fan, and I've read about the dismal returns to taxpayer-subsidized new stadiums despite rosy promises of economic development, and tend to look askance at this kind of thing.

I really like your last point "whatever the computer is telling is true from the computer point of view".

In a surprising number of coding interviews that I've conducted, I've seen a candidate write an incorrect solution that generates an exception and then attempt to figure out the error almost on first principles, rather than actually reading the exception carefully and thinking about what coding errors could have caused it to happen. The exception message is a _huge_ hint!

It's a red flag to see someone try to debug without paying attention to it. Conversely it's very positive to see someone encounter one and then think carefully about it. Writing an incorrect solution but then testing it out and showing the ability to debug and fix it systematically and expediently is no worse than getting it right on the first try, in my book.

I like that Victor Hugo's 19th century version of "deleting apps from your phone" is "deleting your clothes".

I have found that an easy, milder nudge, for either computer or mobile device, is to remain logged off of things by default and explicitly log out whenever you're done.

In what may be a case of Baader-Meinhof, I just came across the term "Whiggish" for the first time, reading Steven Weinberg's _To Explain the World_ (pretty good so far). He also has a dig at Kuhn, recounting a time when they met briefly and Kuhn gave a defense of Aristotle that he found incoherent.

I'm no expert in the field of scientific thought, but my sympathies fall with Morris and Weinberg and the like. I agree with Weinberg that Aristotle understood physics worse than many schoolchildren do today. Which is not to say that Aristotle was stupid, but just that your knowledge is a function of the times you live in and the volume of past human thought you've had the privilege to learn from.

There are legitimate social and ethical concerns for everyone to keep in mind with the advancement of scientific knowledge. But this shouldn't be conflated with the idea that we don't understand the natural world better than we used to. We do.

This one https://apps.ankiweb.net/ or this one? https://www.ankiapp.com/ If there is much of a difference?

I'm in the middle of auditing the Scala track on Courersa.

The first course was great. I agree that Odersky is a very good lecturer, organized and easy to follow. I'd recommend it to anyone interested in Scala.

The second course was OK but not quite as good, it felt a little less systematic. It was mostly Odersky, but for part of the final week the course switches tracks to a different lecturer who clearly was preparing slides for a different lecture series, and I thought both the lectures weren't as clear and the stitch-in of the different material wasn't handled smoothly.

I've just started the third and while it's not Odersky, the lecturers have been good so far.

I like the idea of having a centralized exchange for buyers (readers) and sellers (writers). I would actually prefer it to be variable-fee rather than flat-fee, with buyers paying per article, and the exchange truly playing the role of an _exchange_, taking a commission per transaction.

There's still room for publishers, in the form of editing, curation, and financial support - say, funding a correspondent's trip to a war zone. I'd be fine with some of the price, ideally a transparent amount, going to publishers (or labels or guilds or whatever you want to call them).

The comparison with Spotify is interesting, because I would prefer Spotify to be this way too, and I say this as someone who uses Spotify very regularly. From my (admittedly non-firsthand) knowledge, Spotify has a kind of swap going on between listeners and artists/rights-holders where they take a fixed stream from listeners and pay variable streams to artists. (Although the variable leg is a percentage of the total fixed payments, so in aggregate Spotify pays a fixed leg and there's never a financial mismatch for them.)

At such small payment scales as "price of a song," I don't object to variation in payment being passed through to me. Spotify can take a cut for providing delivery and the app. If I feel like I'm spending too little or too much per month on music, I can scale my use, much like other expenditures in life. My inclination is to feel similarly about print media.

I have sometimes looked at old cinema and wondered, "Why did they make so many Westerns?" I figure that in some decades people will be looking at our time and asking, "Why did they make so many superhero movies?"

Awesome! I did notice when doing the Spanish tree that I recognized a lot of words just from seeing them around the city, especially from ads and public service announcements on the subway.

I've done the Duolingo Spanish tree, and my feeling was the same as the author's regarding "% fluency," which I thought was kind of a joke. Especially for speaking and listening, there's really no substitute for immersion and real-life regular interactions.

But I do feel that Duolingo was honestly pretty good about helping me to read and write. In NYC there's a little ambient Spanish everywhere and I went into it not with the goal of being fluent, but just being able to read signs and understand a little bit here and there. (I haven't kept up with it and now I've forgotten a good chunk, but I'd say that's a different issue.)

At least in my case, it's also been a good entry point because it's free and convenient. I'm actually working on Duolingo's in-beta Czech tree (significant other's family is partially Czech) and it's actually been an inspiration for me to inquire about in-person classes, especially knowing that if I ever want to hold conversations, I will need to have real-life speaking experience. I probably wouldn't have done this if I hadn't started off on Duolingo and had some fun with it!

I think I understand what you're trying to get at, but I don't think describing a p-value in terms of "pure noise" is quite right. The null hypothesis may well carry with it all sorts of specific assumptions: independence, finite variance, maybe even specific probability distributions (and not necessarily the normal distribution). Typically somewhere in there we define a θ parameter and then include something like θ = 0 that provides grounds for possible rejection. We think of "θ = 0" as the null hypothesis, but all the other assumptions are part of the null hypothesis as well; the statement "θ = 0" does not make sense without them.

It seems like it can be construed as a cash handout to owners of BTC, not a spinoff. At least there seems to be disagreement elsewhere on this thread, and from Levine's article.

I don't think refusing to require shorts to deliver BCH opens the door to any other complications. In fact, I think it's the simplest interpretation. You borrowed one BTC, or share, or pony, or whatever, and later you have to return one BTC. If someone else starts a new currency, fine, but that's nothing to do with your borrowing agreement. There's no mention of the price of anything; for all this simple agreement knows, BTC is the only asset in the world. (Though in practice I'm sure you'd have to post margin. Maybe some ponies?)

For shorting stock, the return of dividends and spinoffs is, I believe, a consensus agreed upon by the market as more closely reflecting what people would want - you can start a different stock-lending market that doesn't do this, but there doesn't seem to be much demand for it. To draw a clean analogy between BTC and an equity spinoff, you have to suppose this kind of agreement exists and the contracts signed. I'm not sure what it is that BTC shorts agreed upon, and it seems there isn't widespread agreement, but to me, the simplest and narrowest interpretation of a short, in case of any confusion, is "I borrow 1 BTC, I must return 1 BTC."

(Again, I have no BTC experience, just finance experience, so if someone out there really is short BTC and has wrangled with this stuff, I'd be happy to hear from them.)

I'm not knowledgeable about BTC; this is the part that confused me. If you short a stock, and it distributes dividends or stock or ponies, as Levine says, you have to return that to the borrower. I'm not sure if this is law or just the overwhelming common practice of the markets, but either way we agree on this. You _could_ devise a short agreement where you say "no distributions are owed," but that's not the standard that the big securities-lending market has settled on and I'm not sure why people would demand that instead.

If on the other hand you short a stock, and a third party says "Hey, I'm going to give everyone who owns this stock on this date a bag of cash!" I don't think that shorts would be obligated to cover that. This is, I guess, like what happened with Dole, except that there the third party was a judge, who has the force of law at his back. And this strikes me as similar to what happened to BTC/BCH, except without said force of law. Wherein lies the ability of someone to compel a BTC short to now owe BCH too? What exactly is it that shorts have agreed upon to return to the longs that they borrowed from, and if it's just BTC, isn't returning a BTC enough? If not, what stops someone else from making their own fork and compelling shorts to come up with that too?