You're reading: cp's mathem-o-blog

This matrix joke is only barely worth your time

If you see me doing a maths thing, I’m probably wearing one of my maths t-shirts. I’ve got quite a few, but the one that reliably produces the much-sought-after look of total indifference even once I’ve explained the joke is this one:

Photo of a t-shirt with a drawing: 4 by 4 matrix with N E R D along the diagonal

It’s a NERD identity matrix, get it?

That t-shirt was made by Festival of the Spoken Nerd, and by the way they’ve recently put together some new designs.

It’s long bothered me that the nerd identity matrix contains so many zeros. It’s also only an identity matrix if $N = E = R = D = 1$. Surely there’s a joke matrix somewhere with a bit more meat to it?

Well, here’s a thing I came up with:

\[ \begin{pmatrix} K&E&E&P&U \\ C&A&L&M&M \\ A&N&D&X&Z \\ M&U&L&T&K \\ I&P&L&Y&D \end{pmatrix} \]

It might make a bit more sense displayed like this:

5 by 5 grid of Scrabble tiles reading "K E E P U C A L M M A N D X Z M U L T I P L Y D"

What’s special about that matrix? This!

The matrix from before, multiplied by the vector "EIGEN", equals 12 times the vector "EIGEN"

The vector “EIGEN” is an eigenvector of this matrix, when you interpret letters as their Scrabble scores. Badum tish!

Was that worth the effort? Unlikely.

3 Responses to “This matrix joke is only barely worth your time”

  1. Avatar Henry Ricardo

    I’ve written a linear algebra text, so I don’t find jokes about matrices at all funny. (Just kidding!) Keep enjoying math.


(will not be published)

$\LaTeX$: You can use LaTeX in your comments. e.g. $ e^{\pi i} $ for inline maths; \[ e^{\pi i} \] for display-mode (on its own line) maths.

XHTML: You can use these tags: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>