Comments for The Endeavour

Comment on Nearly everyone is above average by Daniel Lemire

Daniel Lemire — Fri, 03 Jul 2009 16:23:31 +0000

There can be two groups such that when some members of one group are relocated to the other group, both groups’ means are raised.

Right:
A=2,3
B=0,1

Relocate 2 from A to B.

Neat.

Comment on Robust, scalable, and the keyboard works by John

John — Fri, 03 Jul 2009 14:01:19 +0000

Solaris and Ubuntu are not exactly comparable. Ubuntu wasn’t designed to be a new operating system but a distribution of an existing operating system that already had adequate scalability etc. But Ubuntu deserves credit for making the out-of-box experience a priority.

Comment on Robust, scalable, and the keyboard works by gappy

gappy — Fri, 03 Jul 2009 13:03:51 +0000

John, I think it’s not entirely correct to ask how well Ubuntu scales and to say that Ubuntu “cares more about whether the volume and keyboard work than whether the OS scales.” Starting with the second point, check out Ubuntu server, and the many AMIs based on it. In my view, it scales pretty well. With regards to the second point, you can check out the massive Linux clusters deployed by the likes of IBM and Google, which are on par with, or bigger than, most cluster SUN deployments. Blue Gene uses a modified Linux kernel; enough said.

There is no doubt that Solaris, or for that sake AIX, have more sophisticated technology (e.g., containers), but that is beside the point. Linux just works (keyboard included) and has 99% of the features everyone will ever need.

Comment on Three rules of thumb by Jared Updike

Jared Updike — Wed, 01 Jul 2009 20:56:32 +0000

Thanks Bill for sharing that video, and John for adding the link. Made my day.

Comment on Three rules of thumb by Rick Regan

Rick Regan — Wed, 01 Jul 2009 18:23:13 +0000

Re: the video (at about 7:55): A picosecond is a trillionth, not quadrillionth of a second.

Comment on Three rules of thumb by John

John — Wed, 01 Jul 2009 14:39:06 +0000

Thanks, Bill. I updated the post to include the interview you pointed out.

Comment on Three rules of thumb by Bill the Lizard

Bill the Lizard — Wed, 01 Jul 2009 14:16:28 +0000

Grace Hopper gave a fun interview back in the early 1980’s on David Letterman. She explains Hopper’s rule, and even takes it a step further and shows Dave what a picosecond looks like.

Comment on Converting miles to degrees longitude or latitude by Suresh

Suresh — Tue, 30 Jun 2009 23:03:01 +0000

John,
Can you help me converting ***ft North , ****East into degress format ( I mean ** deg.N, ***Deg.E)
Thanks for your help

Comment on Incredibly simple approximation by Sharan Sharma

Sharan Sharma — Tue, 30 Jun 2009 13:39:43 +0000

Excellent post! Thank you.

Comment on Eclectic links by Gene

Gene — Mon, 29 Jun 2009 22:01:58 +0000

Thanks for the entry on SQLite. I keep meaning to look at engine, and then I forget about it and go work with PostgreSQL or MySQL. I know it wasn’t the point of your post, but it did cause me to take action.

Comment on Plain Python by Waldir

Waldir — Sun, 28 Jun 2009 13:59:56 +0000

This post seems to resonate much with (and, in a way, summarize) Eric S. Raymond’s “Why Python?“. It’s much longer, but worth reading. That post delivered the final blow in convincing me to give up my plan to learn Perl (no matter how much I liked working with regex) and try Python instead.

Comment on God is in the details by S.O.

S.O. — Fri, 26 Jun 2009 23:19:09 +0000

“God is in the details” also means that if you search deep enough, then you will be able to discover an aspect of perfection. Everyone strives for perfection, but no one can ever achieve it. So, the only way you can get a sense of what it is, is to search deep enough through all the details of life. At least that’s what I think.

Comment on Sales tax included by John Venier

John Venier — Fri, 26 Jun 2009 18:34:06 +0000

Kevin,

Douglas and Pieter got the answer right. Thanks, guys!

As far as a reference goes, it was in an issue of Games Magazine. They have a web site here. It must have been in a 2008 issue. I believe it was in their “Wild Cards” section, printed on slick color paper instead of the pencil friendly paper they use almost everywhere else. I’ll see if I still have it hanging around. It is usually quite some time before I’m finished with an issue. If not and you need the reference for some reason, I’d imagine the folks at Kappa Publishing (Games’ publisher) would help. By the way, Games is and has been the best puzzle magazine I’ve ever seen. They also have a less-frequently published “Games’ World of Puzzles” serial which is excellent. Anything they make is absolutely top-notch. If I’m not mistaken, even the superhuman and most brilliant Henry Hook used to write for them. If there should be a patron saint of crosswords (especially cryptics) he’d be an excellent choice IMO. If you prefer more logical / arithmetic puzzles check out Conceptis online (from Japan). Extremely good puzzles, and very, very prolific. Plus, they put weekly samples online for free (I think registration is required though). They even send out t-shirts to random puzzle reviewers, but I’ve never got one.

Comment on Four ways to convert Excel tables to LaTeX by ehud

ehud — Fri, 26 Jun 2009 13:36:28 +0000

Hi
I have the same problem getting the error: “compile error: cannot find project or library”. A visual basic screen is opened and the word “CurDir” is highlighted in the code.

Comment on Sales tax included by Pieter

Pieter — Fri, 26 Jun 2009 09:10:10 +0000

Kevin, the caveat is that the relative amount of non-water in a watermelon doubled, while non of it was lost, hence the amount of water is actually halved.

At start, 1% non -water = 10 kilo, at arrival only water is lost, and that 10 kilo is now 2% of the watermelon, so 100% would be 500 kilo. (this of course assumes the 99% refers to the weight and not the volume, but I guess that’s implied…)

Comment on Sales tax included by Douglas

Douglas — Fri, 26 Jun 2009 08:21:16 +0000

At the start:
1000 kg watermelon = 990 kg water + 10 kg non-water

At end: 10 kg = 2% (non-water) 100% = 10 * (100/2) = 500kg

Comment on Sales tax included by Kevin

Kevin — Fri, 26 Jun 2009 02:55:56 +0000

So… a little late here, but any solution or references for the watermelon question?

Comment on Probability mistake can give a good approximation by teknas

teknas — Thu, 25 Jun 2009 23:01:34 +0000

The birthday paradox is a more interesting variant of the problem you introduce. Here you end up picking a pair of people in a room at random and calculate the probability of finding at least a pair of them who share their birthday. Turns out with 23 people you have 0.5 probability of a pair of them sharing their birthday. Not very intuitive but the math is simple and very insightful.

Comment on Probability mistake can give a good approximation by John

John — Thu, 25 Jun 2009 22:33:13 +0000

Good point. Assuming independence in weather reports is unrealistic. Birthdays, sure: independence seems justified, unless you run into twins walking together.

Comment on Probability mistake can give a good approximation by Danny Tarlow

Danny Tarlow — Thu, 25 Jun 2009 22:27:11 +0000

I guess it’s somewhat off-topic, but the thing that always bothers me about using the probability of rain in a given day as an example is the implicit assumption that rain on each day is an independent event. In reality most times, it’s more like there’s a 40% chance a storm will take a certain path through the region, and if the storm does take this path, there’s a near certain chance that it will rain for three days straight.

Comment on Optical illusion, mathematical illusion by John

John — Thu, 25 Jun 2009 19:10:04 +0000

Dave: Good point. I resized the original image, but I should have cropped it. I replaced my first image with a cropped version of the original.

Comment on Optical illusion, mathematical illusion by Dave Richeson

Dave Richeson — Thu, 25 Jun 2009 19:07:35 +0000

That’s a great analogy, John. Thanks for posting it. I’ll have to remember it.

The illusion is really neat too, but one thing that is interesting about the image that you posted is that if you zoom in you’ll see that there are many more than three colors present! I don’t know if you or your blog software made the image smaller, but in the process of doing so, the compression changed the colors of most of the pixels (the stripes are so thin that most of the pixels are on or near a boundary, so they combine the colors in some way). I posted a zoomed-in versions of the original image (the one you linked to) and of your compressed image for you to see.

Comment on C. S. Lewis on reading old books by Jared Updike

Jared Updike — Thu, 25 Jun 2009 18:51:27 +0000

The Practice and Science of Drawing by Harold Speed. Various excellent drawing books by Andrew Loomis (Out of print and available here: http://www.alexhays.com/loomis/ )

Comment on John Tukey’s median of medians by Tim Walker

Tim Walker — Thu, 25 Jun 2009 03:16:08 +0000

A tangent, since I’m by no means a mathematician . . . You may already be familiar with this, but Richard Hamming talked about Tukey’s personal characteristics and work methods in his outstanding lecture, “You and Your Research,” which I’ve cited many times on my own blog.

Comment on Optical illusion, mathematical illusion by Bill the Lizard

Bill the Lizard — Thu, 25 Jun 2009 02:22:23 +0000

I for one would like to hear that in the voice of Lt. Commander Data.

Comment on Optical illusion, mathematical illusion by John

John — Thu, 25 Jun 2009 00:18:24 +0000

The speech software doesn’t read math expressions well, but it does a remarkable job on plain text. I like how it has natural inflection before punctuation.

Comment on Optical illusion, mathematical illusion by Sohail

Sohail — Wed, 24 Jun 2009 23:58:28 +0000

Wow, your blog audio is freaking good.

Comment on Optical illusion, mathematical illusion by Sohail

Sohail — Wed, 24 Jun 2009 23:57:42 +0000

Cool! I can actually see it though if I squint and look at the top of the image. I see two shades of green though, not the same shade.

Comment on Approximate problems and approximate solutions by Phil H

Phil H — Wed, 24 Jun 2009 08:17:45 +0000

One more thing in favour of approximate solutions: they are generally more quickly obtained, so they are usable sooner. If you can discover today that roughly half your customers cannot use your online payment system, that’s worth far more than knowing that 46.2% of them were having problems in a week’s time.

Put another way, Google could sit and calculate exactly the most relevant page it ever found for your search on “first aid cut finger”, but you’d rather have the answer *now*.

Comment on John Tukey’s median of medians by Phil H

Phil H — Wed, 24 Jun 2009 08:06:25 +0000

There are 2 useful things in the ninther concept: approximations to bulk statistics and the calculation of a median without any sorting.

Generalising from 3 groups of 3 to n groups of m, we could still calculate a median from a series of chunks of the dataset, but we would need to sort.

This would suggest problems when working on Very Large Datasets, but consider the case of the most annoying dataset - randomised data. If we take a chunk of data from this dataset, we can approximate the statistics of the bulk with the statistics of the chunk, or a series of chunks.

The answer may be, then, to randomly pick out a series of 9-value chunks, and calculate a series of ninthers. That way the number of comparisons per total values can be less than 1.

O(1) to O(N), depending on how accurate you require your statistics to be.