Calculating Burn Rates in J
hillelwayne.com
hillelwayne.com
Edit: I just re-read my comment and I hope it didn't sound too condescending (not my intent). I'm fairly new to J, but it's pretty cool and I hope you give it a shot if you ever need to do any data oriented tasks.
It's almost better asking where C got the idea that it should be mod from!
While I do appreciate and like both APL and J, I wonder why the author does not (or does he?) use Python + Pandas for this type of calculations.
I'm always impressed to see derivative and both matrix inversion & transpose as elementary operations instead of googling for a library that is most likely poorly documented. Furthermore, since the vector is the basic data type, things like matrices crop up a lot more in J & APL. In Python they are for scientific pursuits. In J they will often crop up even if you're writing a blackjack game. I think this is why it doesn't appeal to many programmers without a strong mathematics background, but it's very appealing to those who have that kind of background and grow tired of writing incessant loops.
Also J is more fun as a puzzle language, so I use it for personal projects. If I was writing stuff for production I'd probably (if begrudgingly) use Pandas instead.