The blog of John D. Cook
From the category archives:
Math and aesthetics
Beautiful architecture video. No explicit math, but lots of math behind the scenes.
Some math and some great images: 3-DSpirographs
Advanced math with some pictures: algebraic topology books for download from J. P. May and Allen Hatcher. (Hatcher’s book has more pictures.)
Miscellaneous
There’s really nothing that cannot be innovatived
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The struts on the LightSail solar sail spacecraft are made from of Stanley tape measures. For details, listen to this episode of the Planetary Radio podcast.
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I was skimming through Big Ideas: 100 Modern Inventions the other day and was surprised at the dates for many of the inventions. I thought it would be fun to pick a few of these and make them into a quiz, so here goes.
Match the following technologies with the year of their invention.
First the inventions:
Now the years:
Two of the years are used twice. Quiz answers here.
All examples taken from Big Ideas: 100 Modern Inventions That Have Transformed Our World
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Better to have a simple system than a complex system with a simple abstraction on top.
Abstractions are never perfect. Every new layer creates failure points, interoperability hassles, and scalability problems. New tools can hide complexity, but they can’t justify it … The more complex the system, the more difficult it is to fix when something goes wrong.
From the preface to RESTful Web Services.
Related posts:
Obscuring complexity
Baklava code
Leaky abstractions
Less isn’t more; just enough is more
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I accidentally pushed “publish” while I was working on this, so here’s this weekend’s miscellany post a little early.
Economics
Market failure and government failure
If you’re paying, I’ll have top sirloin
Engineering
Engineering aphorisms
Evolution of complex systems
Math
World War II mathematician
Packing tetrahedra
Software development
11 wrong programming assumptions
Programmer competency matrix
The greatest program ever written
Classic software development mistakes
Wrong Correctness
Miscellaneous
Some ideas for visualizing knowledge
Why I like Twitter
Rhonda Tiption’s podcast list
15 Awesome Uses Of The Periodic Table
Comparing Avatar and Pocahontas
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Notes on using regular expressions in R. R uses POSIX regular expression syntax by default but you can ask it to use Perl’s flavor of regular expressions.
Related links:
Regular expressions in C++, Mathematica, Python, R, PowerShell
R for programmers coming from other languages
R: The good parts
Daily regular expression tips
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Regular expressions are fairly portable. There are two main flavors of regular expressions — POSIX and Perl — and more languages these days use the Perl flavor. There are some minor differences in what it means to be “like Perl” but for the most part languages that say they follow Perl’s lead specify regular expressions the same way. The differences lie in how you use regular expressions: how you form matches, how you replace strings, etc.
Mathematica uses Perl’s regular expression flavor. But how do you use regular expressions in Mathematica? I’ll give a few tips here and give more details in the notes Regular expressions in Mathematica.
First of all, unlike Perl, Mathematica specifies regular expressions with ordinary strings. This means that metacharacters have to be doubly escaped. For example, to represent the regular expression \d{4} you must use the string "\\d{4}".
The function StringCases returns a list of all matches of a regular expression in a string. If you simply want to know whether there was a match, you can use the function StringFreeQ. However, note the you probably want the opposite of the return value from StringFreeQ because it returns whether a string does not contain a match.
By default, the function StringReplace replaces all matches of a regular expression with a given replacement pattern. You can limit the number of replacements it makes by specifying an addition argument.
Related links:
Regular expressions in Mathematica
Tips for getting started with regular expressions
Languages that are easy to pick back up
Regular expressions in C++, Python, R, PowerShell
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Smashing Magazine highlights (design)
Top 10 algorithms of the 20th century
Why your boss is incompetent (Peter Principle revisited)
Visualizing word frequency in the Bible (word clouds)
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I have four Twitter accounts that send out one tip per day. One of these might help you with a New Year’s resolution. If you don’t use Twitter, you can follow these Twitter accounts by subscribing to their RSS feeds.
Windows keyboard shortcuts
If you’d like to become more efficient in using Windows, and reduce your chances of repetitive stress injury, you may want to use your keyboard more and your mouse less. SansMouse is a Twitter account that sends out one keyboard shortcut per day.
Regular expressions
If you’ve intended to learn regular expressions but haven’t made the time, you might want to follow RegexTip for one tip per day about regular expressions. I focus on the features common to Perl, Python, C#, JavaScript, etc. I also have some tips coming up with language-specific tips.
Math
I have two mathematical Twitter accounts. These might be useful if you want to review math courses you took a long time ago or if you want a preview of math you might need in the future. Both are eclectic, mixing elementary and advanced topics.
ProbFact sends out one probability fact per day, mostly theorems but sometimes notes on applications.
I just started AnalysisFact a couple days ago. It will cover a wide range of topics from real and complex analysis. AnalysisFact will have a wider range of sophistication than ProbFact, mixing undergraduate and graduate level material.
Summary
Here are the four Twitter accounts and their RSS feeds:
New Year’s links
Here are a couple posts from Jon Swanson:
8 ways to end the year
Leave it in 2008 (Just mentally change the “8″ to a “9″ when you read it.)
And here is a good post from Jurgen Appelo:
Checklist for goals and resolutions.
Related posts
Using Windows without a mouse
Tips for learning regular expressions
Math and statistics articles
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Here’s a list of 19 “why” posts I’ve written.
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How start-ups turn into bureaucracies
Top 50 health informatics blogs
Best end user license agreement (EULA)
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A few days ago my family and I went to see a stage performance of Charles Dickens’ A Christmas Carol. For years I’ve glossed over references to money when reading British literature but I’ve intended to figure out how it all worked before decimalization. Watching A Christmas Carol prompted me to finally do it.
Many thanks to my British friend Samuel Jack for helping me sort things out. Any errors in this post are mine and not Sam’s. If you find an error or omission below, please leave a comment.
The most basic denominations were pound, shilling, and penny. The pound and shilling had the nicknames quid and bob respectively. (The plural of “penny” is “pence.” The terms “quid” and “bob” are both singular and plural.) A pound equaled 20 shillings and a shilling equaled 12 pence. Pound, shilling, and pence had the abbreviations “L”, “s”, and “d” which came from the Roman librae, solidi, and denarii.
A florin was two shillings and a crown was five shillings. A guinea was 21 shillings. (The reason a guinea was slightly more valuable than a pound had to do with precious metal exchange rates.)
A few more denominations were self-evident. For example, the half crown and sixpence were worth what you’d think.
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Last year I wrote a post about my favorite audio book narrators: John McDonough and Rob Inglis. Here are three more who came to mind lately.
Related posts:
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Creativity
Removing barriers to creating amazing things
Tech
The best and worst tech of the decade
Visualizing browser market share over time
Math
The rise and rise of Python in computational science
Why exponential growth is big (cartoon)
Math teachers at play #21
Probability of identifying someone given their age, zip code, and gender
PowerShell
Science
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