Month: August 2011

Perverse hipster desire for retro-computing

Posted on by John

Here’s my favorite line from an article Life on the Command Line by Stephen Ramsay:

I also don’t do this [work from the command line] out of some perverse hipster desire for retro-computing. I have work to do. If my system didn’t work, I’d abandon it tomorrow.

That’s refreshing. Some of the more ardent command line advocates give the impression that they use the command line out of pride rather than out of a desire to get work done. Ramsay is recommending his way of working, not bragging about what he’s able to do. He has some interesting ideas, especially in his follow-up article The Mythical Man-Finger.

By the way, I’m no command line wizard; I’m a fairly typical computer user. On the other hand, my use of the command line and Emacs has been increasing.

Related posts

Like putting a coke machine in a monastery

Posted on by John

When someone suggested to Derek Sivers that he cover the CD Baby website with advertising, he replied

No way. Out of the question. That would be like putting a coke machine in a monastery.

I love that simile for something highly inappropriate. In context, I believe Sivers was saying that advertisement would be an inappropriate way to make money given his vision for CD Baby. But I think more of the disregard for aesthetics and historical context. I could just imagine how crass a coke machine would look in a medieval stone building, something like putting a glass and steel pyramid in the courtyard of a French Renaissance palace.

Derek Sivers’ quote comes from his new book Anything You Want.

Few coefficients, few roots

Posted on by John

Here’s an elegant little theorem I just learned about. Informally,

A polynomial with few non-zero coefficients has few real roots.

More precisely,

If a polynomial has k non-zero coefficients, it can have at most 2k – 1 distinct real roots.

This says, for example, that a polynomial like x100 – 12 x37 + 1 can have at most 5 distinct real roots, even though it has a total of 100 roots when you count complex roots and count with multiplicity.

I won’t repeat the proof here, but it’s not long or advanced.

The upper bound 2k – 1 in the theorem is sharp. To see this, note that

x(x2 – 1)(x2 – 4) … (x2 – (k-1)2)

has k non-zero coefficients and 2k – 1 distinct real roots.

Source: Mathematical Omnibus

Update: Someone asked about the converse. Does having few real roots imply few non-zero coefficients? No. The polynomial (x2 + 1)n has no real roots but it has n+1 non-zero coefficients.

RLangTip changing hands

Posted on by John

I’ve decided to hand my Twitter account RLangTip over to the folks at Revolution Analytics starting next week. I thought it would be better to give the account to someone who is more enthusiastic about R than I am, and so I offered it to David Smith. If you’ve enjoyed RLangTip so far, I expect you’ll like it even better under new ownership.

If you’d like to continue to hear from me on Twitter, you can follow one of my 10 other daily tip accounts or my personal account.

Descriptions of these accounts are available here.