6,596 karma · joined February 20, 2007
To whomever that has read upto here: you hereby implicitly agree my EULA, in which you swear to enjoy each of your scientific pursuits with intensity and to your fullest degree; and sometimes even to a dangerous degree, if the mood carries you thus. Additionally, you agree to never allow an employer, family member, or any other authority to break your intrinsic spirit; for they have no means of dominating your spirit except that which you subconsciously allow them. You shall be true to yourself and to your own principles, regardless of society (though in privacy). You shall hereby refuse to believe any scientific statement as "true", however benign, except those in which you alone have proven to yourself to be true, by your own hand and evidence. (Though it doesn't hurt to check out what other people have to say on the subject, from time to time; in fact, it turns out to often be a more valuable course of action, for the careful analysis of a close friend can often reveal subtle flaws in your process and in your logic, while occasionally forcing you to re-evaluate your core reasoning for choosing that process in the first place, which always leads to the path of learning and thus improvement and satisfaction.) You agree to eventually die with no regrets. Let no one impose themselves upon your judgement without merit. You shall endeavor to enjoy life to the fullest extent of the law (where applicable), and to realize that money is merely a means, not an end unto itself. In your spare time, you shall research that which is impossible, but intriguing, in order to always have something to strive for, thereby improving your skill and your spirit. You shall follow your curiosity wherever it leads (but keep both eyes open for signs of danger).
Most importantly: thou shalt enjoy every week, else thou shalt fix your life's situation regardless of how immutable it may seem.
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We need to call our congressman and speak to whomever is on the line, with our voices. Not pens or keyboards.
When your congressman asks his staff "What have the public been calling about?" (which he asks regularly), then there's a good chance that SOPA will be mentioned.
But only if you call your congressman!
We need to call our congressman and speak to whomever is on the line, with our voices. Not pens or keyboards.
When your congressman asks his staff "What have the public been calling about?" (which he asks regularly), then there's a good chance that SOPA will be mentioned.
But only if you call your congressman!
For the curious reader, here's how to do Java entirely from the command line:
1) install the JDK and add its "bin" directory to your PATH. For me this was "jdk1.7.0_02/bin"
2) copy and paste http://pastebin.com/R47bwDZx and save it into a new file called "test.xml"
3) copy and paste http://pastebin.com/Ut5dKBkn and save it into a new file called "ReadXMLFile.java"
- note, this is not my code. It's just a snippet I found from the 'net. Feel free to clean it up. =) My goal was "to get up and running as quickly as possible". Production code would be cleaner than this.
4) run these commands:
javac ReadXMLFile.java
java ReadXMLFile test.xml
So why go through all this trouble, when you could just write it in Python?
Deployment comes to mind as one reason to go with this approach; fewer systems have Python installed than Java runtime.
So therefore when you deploy your app, you'd have to either 1) make customers install Python, or 2) (more likely) ship the contents of the "Python27" folder along with your Python app, and invoke your app via a shell script, or something. I'm not sure.
I have no idea, but is it reasonable to make the claim that the DMCA is flawed? By that I mean, is it excessively annoying / ineffective to actually use the DMCA for its intended purpose?
(I'm not referring to DMCA abuses... just whether it's fundamentally broken or not.)
I haven't really given it much thought. I always assumed that the DMCA was a reasonable middle ground. But is it?
...but I see no way to actually do that. Does anyone else? Where are the kits?
Paul worked very hard to grow Viaweb for several years, and eventually guided Viaweb to a lucrative exit via Yahoo.
Arrington worked very hard to grow TechCrunch for several years, and eventually guided it to a lucrative exit via AOL.
"And you'll see listed here are a number of boot images. Each one of these boot images contains the configuration of a kernel that will probably match one of your systems. Let's go ahead and use the DOS program 'edit' to view the images.idx file now."
"Here it shows in the left hand column the last four numbers of the boot images of the files we just saw earlier. On the right side is a description of the type of system we need to install it onto. For example if you look on the first line it'll show that it has IDE/ATAPI or SCSI. In other words if I take the boot image 0000 then I will be able to utilize the boot image on a system that has an IDE CD-ROM drive."
Heh. It sounds like installing Linux was as easy as 0001, 0002, 0003...
For example we can visualize "taking the derivative of the function f(x)" by "rolling a wheel over the top of its graph": http://dl.dropbox.com/u/315/random_pics/derivative_wheel.png
The red circle is a "wheel" which happily rolls back and forth along our f(x) graph. The green line is the derivative of f(x). It's intuitively obvious what that green line is -- if you had to fit a flat piece of paper between the wheel and where it touches the graph, then you'd get that line. That's the derivative, also called the "tangent line" or "slope of the graph" at that point.
(The wheel will always touch the graph only once, because we can visualize it as small as we need it to be --- infinitely small, even.)
It's common knowledge that a curve's derivative is zero at its maximum / minimum. (In other words, "when the wheel reaches the top or bottom of a 'hill', then its derivative is zero, aka the tangent line is perfectly horizontal".) So right away, we immediately understand where the zeroes of the f'(x) graph must be located.
But the real power is, we also have a rough idea of how the f'(x) graph must look, by "watching the wheel's tangent line as we roll it along the graph", in our mind's eye.
So that's a neat trick, but why does it matter?
Well, here's one example: It's the most natural and obvious thing in the world that the derivative of cos(x) is -sin(x).
http://dl.dropbox.com/u/315/random_pics/derivative_wheel_cos...
We start at x=0; we see that the wheel is "resting on the very top of the slope", meaning the tangent line is flat, so we know right off the bat that the derivative of cos(0) is 0.
From there, the wheel "rolls downhill"; therefore the derivative "goes negative"; and it goes back to zero when the wheel reaches the bottom of the hill (which we see is at x=pi).
The wheel then begins climbing uphill, so its derivative "goes positive"; and it goes back to zero when the wheel reaches the top of the slope (at x=2pi).
So we see that the graph of the derivative of cos(x) has zeroes at 0, pi, and 2pi; and we also intuitively understand that it's negative from 0 to pi; and we see that it's positive from pi to 2pi.
Now all that's left is to think about the graph of -sin(x). It's exactly what we just described: zero at x=0, x=pi, and x=2pi; negative from 0 to pi; and positive from pi to 2pi. So that's why "it's obvious to us that the derivative of cos(x) is -sin(x)", QED.
So if you've had to worry about rote memorizing those sorts of formulas, I'd urge you to give these visual techniques a shot. You'll never again need to memorize seemingly-arbitrary equations, which is pretty sweet IMO.
Sorry for rambling on; I just get so excited about presenting math "in a visual way". It's a lot of fun, and likely wouldn't hinder the ambitious mathematician at all --- just the opposite, in fact: Feynman, for example, had an arsenal of similar techniques, which probably contributed to his intuitive understanding of the physics behind the formulas and his ability to "see past" the raw equations.
For example: when I think of "x times y", I picture a rectangle whose sides are lengths x and y respectively; so naturally, the area of the rectangle is x times y.
Next time you come across an equation similar to "(x0 + x1)(y0 + y1)", you might try picturing it like this: http://content.screencast.com/users/shawnpresser/folders/Jin... ... you'll discover all kinds of interesting things. E.g., Karatsuba noticed that (x0y1 + x1y0) can be computed as follows: "Find the area of the entire rectangle (x0 + x1)(y0 + y1); then subtract the area of the purple rect (x1y1); then subtract the area of the gray rect (x0y0); thus giving the answer." This was a major breakthrough in mathematics at the time, because it meant you could calculate the product of two arbitrarily large integers with N digits in less than N-squared time: http://en.wikipedia.org/wiki/Karatsuba_algorithm (and http://dl.dropbox.com/u/315/books/Karatsuba%20Algorithm%20%2... was his original paper).
Another random example: Have you ever played the game "pipe dream", where you have to connect the pipes together before the liquid fills them up and spills out? Well... the way I visualize "integrating a function" is: imagine the graph of the function. Now start "filling up the graph" from left to right --- just like Pipe Dream. The answer is: the total volume of the "liquid" above the zero line, minus the volume below the zero line. http://upload.wikimedia.org/wikipedia/commons/9/9f/Integral_...)
Visualization tricks are a great way to get a "gut feeling" about "what does this equation actually mean? e.g., how might I relate the equation to some real-world (or imaginary-world) phenomenon?" ... you just have to be careful that your visualization is exactly equivalent to the mathematics, since an inaccurate visualization would throw off your intuition.
I've never seen anything like this --- an accurate 3D model of a brain, which you can click and drag to rotate. This has a lot of educational value. (Apparently, static 2D images of the brain on Wikipedia et al don't really give you a good "volumetric sense" of what the brain looks like.)
My only wish is to be able to "highlight" the various structures of the brain, e.g., the Hippocampus, to know where they're located / how big they are in relation to the whole brain.
Bravo. Wonderful work.
But! I present, for you, my next best effort, "YearlyKitty": http://dl.dropbox.com/u/315/random_pics/scuzzle.JPG
Thanks for everything you've done Colin. I hope you're able to maintain your drive and ambition throughout your lifetime, and I look forward to seeing "your next thing", whatever it turns out to be. (For example http://www.daemonology.net/papers/cachemissing.pdf was especially cool IMHO, but all of your projects have been interesting.)
That's brilliant. Anyone know if this has ever been tried?
If $0.01 is all you can afford, there's no shame in it.
When you click the up/down arrows, it sends the vote in the background, using javascript.
So if you upvote + immediately refresh, that will cause the javascript submission to cancel, thus the vote won't count. (e.g. when you refresh a page, any async javascript queries which haven't yet completed will be canceled due to the refresh.)
#2:
Your average karma is the average of your 50 most recent comments. However it's only recalculated every so often. Specifically, each time you click the "add comment" button, there is a small random chance that your average karma will be recalculated right then.
e.g. the act of writing a comment is the trigger for recalc of avg karma; but it doesn't recalc every single time you write a comment --- rather, only every ~20 comments or so. (HN does this because it would be prohibitively expensive to recalculate avg karma for every user for every comment.)
So it's likely you had an avg of 1.64 in the past, which dropped to 1.0 over time, and that fact only became visible to you after your recalc.
The "Shark Week" ad that literally screamed at me at 11PM was the straw that broke my mental back. I immediately installed AdBlock.
iPhone knows your latitude and longitude --- your position on the surface of the Earth. It also knows the location of each star. Lastly, it knows which way your screen is pointing.
That's all the knowledge that's needed in order to display a starfield on the screen.
I haven't paid the collectors.. I've been so disgusted with the situation and their behavior.
Again, thank you so much for your time.
I love toast.
If my car dies, I won't be able to get anywhere, because I can't get a loan for a new one.
When we move to a new apartment, they won't allow us to have Internet service. I am not exaggerating in the slightest. AT&T U-Verse already denied me once in the past, before I got my score to 760 --- they refused me service. Completely. No alternatives. It didn't matter to them whether I had $10, $1,000, or $10,000 in the bank. The computer told them "unknown risk", and so they would not do business with me. There were no alternative internet providers. I would have been completely screwed, but my wife (who was my fiancée at the time, thankfully; credit score of one person will reflect on both of you after marriage) was approved.
We will not be able to get a house, if we choose to. We might not even be able to live in a specific area we want --- apartment complexes check your credit before allowing you to live there.
All over $80, due to the messed up health insurance system. Blergh.